The more severe software problems are usually caused by a hardware failure. No start (with or without an error message), frequent crashes with different errors each time, frequent freezes or Windows running extremely slow all indicate hard disk, memory (RAM), motherboard or overheating problems. If you have used the recommendations for setting up Windows with two accounts, the chances of having viruses or spyware are very slim.
The most common software failures are caused by viruses and spyware. The computer is running slow, Internet doesn’t work, there’s an icon next to the clock that tries to scare you into buying some kind of “antispyware”, Internet Explorer doesn’t work, when you try to start a program it takes more than a minute for it to appear, etc.
The other common cause of software problems is when updating or installing a new driver or a Windows update. In these cases the fix is easy: restart the computer in safe mode and use Windows’ build in System Restore to undo the last installation/update. If the computer doesn’t want to start in safe mode, Windows has to be reinstalled.
There are two ways of doing this:
Try to remove all viruses and spyware, although there are some really nasty trojans and rootkits that are almost impossible to remove. This method seems faster and easier but it can take from about two hours to over six hours.
Reinstall Windows. Backup your files, reinstall/restore Windows from the CDs that came with the computer, then install back all the programs you use and copy back your files. This method will probably take at least three or four hours and you will have to redo all custom settings you have in Windows and in the main programs you use. The advantage of this method is that it will take care of all software problems you may be having and your computer will run faster at the end.