In general, Windows may be able to help you with unwanted changes on your system. Try:

START-> Programs-> Accessories-> System Tools-> System Restore

Make sure "Restore my computer to an earlier time" is the selected task

Click "Next" down below

Click on a date on the calendar when things were running good (has to be bold faced)

Click "Next" down below and follow through with the restart.

This should help with your latest snag. Just be sure you have system restore points (that's boldfaced dates on the calendar for you losers like Stuart) established as free insurance against time-comsuming hunting trips for malware