Well, consider trying Ubuntu:
http://www.ubuntu.com/
It's an open source free operating system and virus' and bugs that torment Windoze, don't touch any linux. You need not give up windows, you can dual boot.
FYI all Linux software is free and very powerful, including Firefox(web browsing), Open Office (powerful and compatible with Microsoft office) and Gimp (Photoshop). With Ubuntu most of it comes with your OS, plus drivers for your computer, anything else you want you download for free with a 'software update' interfect, very easy.
Back to Windows XP:
A couple things could be going on. A virus is possible, a child with root access randomly deleting system files, or even a dying hard drive.
First thing, back up all your important files.
Use a virus checker, this free one,
http://free.avg.com/us-en/homepage , is better than many commercial anti-virus programs.
Boot from your Windows installation disk or a hard drive repair disk, you want to evaluate your hard drive from a disk check and repair program running from your CD or DVD so the entire hard drive can be checked. If the program reports much of your hard drive is ruined and cannot be repaired, it means you need a new hard drive, not just a fresh OS installation.
Of course the best solution for a clogged WINDOWS system is not just to reinstall Windows, but to REFORMAT the hard drive (which will not fix a dying hard drive, but will destroy incubating computer viruses) and then reinstall Windows. Back up all your favourite files and make sure you have installation files for your important software first.
Any hardware driver you're missing can usually be downloaded online. Type the manufacturer name and then "sound card driver download" in google and it should take you to where you can download the driver directly.