One of the problems with Windows, in general, is its stability and security problems. One of the causes of stability and security problems is the need for Windows to support various versions of different software, its own as well as third party products.
Periodically, Microsoft issues rollup updates, which give it a baseline to work from when supporting their own product. SP2 was one of those rollups. By continuing to use Windows SP1, and by possibly encouraging others to do so, you are requiring useless complexity in Windows.
Now, any pretty good knowledge of computer security is a good start, but any real knowledge will tell you that keeping your computer up to date is essential.
XP SP2 has been out for an extremely long time. Its time to put SP1 to bed, and prepare for SP3 or Vista, which ever comes first. As Windows customers move to SP3 or Vista, support for SP2 will continue. But support for SP1 should not.
Move to SP2. Windows is bad enough with it - its worse without it.
Having applied SP2, proceed directly to malware analysis. If you've been running with SP1 this long, you probably have something you're not aware of.
Now if you're reading this specifically because your computer has problems, but you already did malware analysis, yet you can't find the source of the problem, your computer may be now part of a botnet. In this case, the only solution is for you to "flatten and pave".
- Immediately, disconnect from the network.
- Repartition, and reformat the drive.
- Re install Windows XP.
- Upgrade to SP2, and all security patches.
- Reconnect to the network.
I'm aware that this is brutal, and maybe rude, advice. But if you're advised any less, we're essentially saying
Look, you can solve your computer problems without upgrading to XP SP2. It's OK to run XP SP1.
But, it's not OK. Windows XP SP1 isn't supported by Microsoft, as of October 2006. Period.