[Fyron]

If you do reinstall, I'd recommend making 2 partitions, one for Windows (6 GB or so is more than enough for WinXP and page file) and one for data. This way, you can just reformat Windows partition when it inevitably blaws up and not lose any data or programs. A surprising number of programs do not actually need to be "installed" (aka bloating registry) to function properly. You can even use TweakUI (tool provided by MS) to move folders such as documents, start menu, and desknop to the data partition, thus making rebuilding even easier.

Edit:
Also, boot into safe mode. This will stop almost all malware from being able to start.