Restore does not erase your personal files and is reversible.
You can choose the earliest date available, setting the computer back to Day one, if you want to.
click all programs
click system tools
click system restore
check the box that says restore my computer to an earlier time, click next
select a bold date on the calendar, a date before the problem started, click next
follow through with the restore directions
restart the computer after it finishes
if the system restore does not work, select an even earlier bold date on the calendar and repeat the procedure
try this with at least four earlier dates before giving up and trying something else