Well that does look like Windows XP. But let me ask, is it XP, or did you make Vista look like XP?
If it is Vista, then you need to run ET as an admin, if you don't, you'll get the "Failed Pure Server Check" message.
Right click on the ET icon, go down to properties. Under the compatability tab, at the bottom check the box that says "Run as Administrator"
If you are running XP, when did this problem occur? Did you modify, dl/install any new patches, files that would effect ET in any way?