How to trouble-shoot a PC

This guide is under construction. There is a large hole in the middle and it rambles on without a plot. You have been warned!

Finding out what's wrong with a PC can be beyond most people's abilities. The average pc enthusiast will re-install windows at the first sign of trouble. This causes two problems: firstly the user can lose important data, and more importantly, since setting up is often done over a number of weeks,  his set-up never stabilises because he re-installs before he's finished setting up.

Through many unhappy hours repeating this process I have learned a thing or two. You can preserve the state of your pc by not installing any software, once you have everything you need. This means no experimenting with new shareware and no taking the lid off to re-arrange the PCI cards. You can fix some of the problems that defeat many users, putting off the day you get out the install disks.And finally you can take some shortcuts with the re-installation if the need arises.

OK now before I try to solve all your problems I need to explain what goes on inside a PC so that you can make the correct decisions about what's wrong.


Many items of hardware within your pc require resources, that is, one or more items from the following list:

What these things are is not important to the user. What is important is that conflicts do not occur.

Conflicts occur when either windows, the bios, or the hardware itself allocates the same resource to more than one device. This issue is complicated slightly by the fact that some hardware can break this rule and share the same resources with others.

The way your assignments are made depend largely on the bios. AT boot-up time the Bios examines the system and assigns resources as required. The list of assignments is passed to windows as it boots up and in some systems may be modified from within windows. In others it is necessary to make any modifications from the Bios set-up screen.

Now the reason conflicts occur is that there are often not enough to go around. The worst offender in this respect is Interrupts. There are only 15 of them and most are grabbed for use by the system. This means that when you come to plug in expansion cards, you may run out of them.
My own system has four PCI slots, and the Bios assigns slot 4 to the same interrupt as that used by the PCI bus, and slot 1 to the same interrupt as the AGP graphics card. This has implications for anything I plug into those slots. Similar compromises appear on all motherboards.

Compounding the resource assignment issue are add-on cards which are either plug and play (that is, automatically assign resources), non plug and play, or somewhere inbetween.

To examine your hardware set-up, use the system properties window within control panel. If you click on the device manager tab you will see a list of hardware which windows has installed. If you are in Safe mode, what you see is a list of all the available drivers in the computer. Otherwise you only see the devices which are actually present.This is because in Safe mode Windows does not try to detect the hardware.

Looking down the list, any conflicts will be signified with either a yellow exclamation mark or a red cross.

If you pick on an item of hardware and look at it's properties, you will be able to see which resources have been assigned to it. If Windows has detected a problem it will display a message explaining which items are conflicting and with what.

For an overview click on the Computer icon right at the top of the list. Here you can choose to see a list of any of the four resource types and which hardware has been assigned to it.This is a good place to look for multiple assignments. Even if no conflicts have been detected, multiple assignments can cause problems.

Causes of trouble

Now there are two reasons why a computer is having a problem:

And there are two ways that your pc could be failing:

Failing to run Windows from day 1

A pc which won't run a standard fresh install of windows is likely to be suffering from a hardware-related problem. However there is one possible cause which is software related: Did you re-install after making a copy of your old windows directory somewhere on the disk? If so, windows will have found and copied all the old settings from your backup. The solution here is to take your backup off-line during the installation.

Assuming you really did do a fresh install, your problems are likely to be connected with the BIOS set-up, or with bad hardware .

Problem types

Solving catastrophic failures

To eliminate the cause of the problem, you must reduce the computer to a minimum set of components:
Remove any add-on cards, except the graphics card
Remove any extra hard discs or cd-roms, leaving just one floppy, one hard disc and one cd-rom.

Now re-start the computer and look for the problem

methods of attack

determining the cause


mention regrepair / regmedic

common faults and fixes


These are the most common faults:

There are 16 interrupts, many of which are used by the system and some are free for add-ons. Most active devices should have one and Windows will conspire with the bios to arrange them in working order. The same is true for the I/O ports, DMA channels and memory map. However, this automatic selection or plug & play as it is better known, can go wrong for a number of reasons.
When you switch on your PC, the BIOS detects the plug and play cards and assigns resources to them. It also assigns resources to internal devices such as ports

Windows sometimes chooses the settings incorrectly, so it's up to you to manually alter it's choices so that no conflicts exist. To compound the problem, some add-on cards cannot be configured directly from Windows. This means that as well as adjusting the settings, you may have to either run a separate configuration program or pull out the offending card and change some jumpers. Be aware that changing a setting in control panel may not change the board's setting to match

A conflict can sometimes occur which Windows cannot detect. This will show itself in the form of random crashes or corrupted screens and is caused by one of the following:

Try re-installing the software. Faulty driver software can usually be replaced by searching the internet for the latest version.

If you have a piece of hardware which doesn't show up in the device manager, disconnect it for a while and see how the computer behaves. If the problem goes away, you may have to replace the device with a more recent model, but try searching for an updated Windows 95 driver first.

General device driver advice

Some motherboards are supplied with a disc containing IDE bus drivers. If your computer is working without problems and you have not yet installed these drivers, I recommend that you don't. More often than not I have had to start all over again because these caused windows to crash. However, if you have a Bus Master driver and system devices does not indicate this, then you may get a speed improvement by installing. Be prepared to throw away all the software installation you have done and start again.

Most device drivers can be changed at any time; however the display driver is a problem as removing it could leave you with no display. Accordingly you should change to the standard VGA driver, re-boot and then change to the new driver.

If a device appears in a category called "Other devices", it is (usually) incorrectly configured and needs a driver. In some cases you may appear to have two identical conflicting pieces of hardware when in fact you have two drivers loaded for the same device. remove both and re-boot, windows should re-detect the hardware.

Windows 95 has a special operating mode called "Safe" mode. This allows windows to boot with minimal settings so that changes can be made to the set-up. Safe mode can be entered at boot-up by pressing F8 when you see "Starting Windows 95".

Add-on cards which are not plug and play can cause the computer to crash before you get around to setting them up. The solution is to install these last, and ensure that you choose interrrupt and I/O settings which do not interfere with the other devices already present.