Could you offer more detail on the filenames Spyware Doctor is alerting as infected (i.e. The path and name)?
Whenever I've run Spyware Doctor in the past it always seems to come up with SOMETHING, although a lot of the time it's things that are not really dangerous, or could be solved by simply emptying your cookies rather than paying 20bucks for them to do the privelege. I'm not saying they're scamming (I'm more than sure Webroot is a legitimate company) but would probably consider their techniques of scaring people into a purchase a grey area...