Question about CC fraud and reformat

I recently had an issue where somebody got a hold of my CC# over the internet and charged a small amount (like $100). I went through the step-by-step of cleaning the malware off the computer. It checked out fine. I was planning to do a reformat of the computer before this all happened so I could start fresh and also put a small partition for just the OS. The computer has stuff on it from the last 2 years and I have backed up everything I want to keep.

I was just wondering if reformatting does anything to get rid of malware that the cleaners did not catch? This would not decide whether I reformat or not. Just a question. Also when I make the partition, what size should it be for the OS. I have an 80 G and I run XP home. Thanks!

 

Thanks!

 

BTW, I do use AVG, Zone Alarm, CCleaner, Ad-aware, and Spybot. But I don't use any of the "protect my computer form spyware" apps like Spyware Blaster. I'll start using those as well.