Next time you reformat (make sure that you always do this), unhook your network or internet cable. you obviously have sp1 (it wouldn't happen with sp2). install your spyware and A/V and firewall before you connect it back up. and disable window messenger (you can also do it in start, run services.msc)
Since you don't have too much stuff on it now. it is better to reformatt it. it will only take 20 minute to an hour to do. delete the hard drive with powermax and start over. then you will know for sure that you are clean.
and follow the above advice about the network, you are at you most vulnerable at this stage (having internet hooked up while reformatting)
sometimes it is better to build a new ladder than patching the broken one