i suggest you reprogram the whole thing, save your files in a cd...
before everything gets so so irreversible..
This is an action of last resort. The problem is that while you can save your documents to memory stick (no need to use CDs any more) you cannot save your installed programmes, drivers, registry settings etc in the same way. (Unless you use a disk imaging programme such as Norton Ghost or Acronis True Image).
Modern anti-viruns and anti-spyware/malware programmes will generally find and destroy most threats, although a few tricks may be necessary in order to get them to run. New out is Microsoft Security Essentials, which is free and seems to be as good as or better than some of the paid-for AV suites.
Please do all continue to post computer-related problems here and I will help whenever I can - as will others, there are more than me who read this who have 'the knowledge' and a bit of computing nous. Don't rush off to implement any old advice such as that given above however, as if you are not sure what you are doing you could end up with a dead lump of plastic and silicon instead of a PC.