Originally Posted by Izagaia
Well... the thing is that once you wipe your harddrive clean and reformat (re-installing a fresh copy of your OS in the process) you are doing just that; "erasing all data on the current partition, including your registry, and replacing it with new code".
I do not know exactly how many partitions your system has or if it is possible for malware to actually "jump" from one to the other, but if you are installing an anti-virus application IMMEDIATELY after reformatting (even before registering the key with Microsoft, then I do not possibly see how your system could become infected like you are describing to reject that AV application. I just do not think it is possible for your system to become infected if you have taken every step to stay offline before you can put up a solid defense.
I suppose at this point, I would have to wonder if you are using a "true" copy of Windows XP or one of those bloated OEM versions (usually the case if you bought your system from a local retailer such as Walmart, Best Buy, Circuit City...etc) which contain the OS and every crap piece of third-party trial, partial and half-assed versions of other worthless softwares bundled in on the planet? In which case, did you actually perform a "reformat" using the Windows CD or merely one of those "Quick Restorations" using a disk that came with your system which restore it to the factory settings?
Big difference between the two in terms of what you are actually placing within your system.