System restore will delete the files I downloaded?
No. It will save everything you DL, your DL's and data files and personal stuff are unaffected..
It will also preserve all your programs and settings that you had BEFORE the restore date - choose a restore point just before the problem started, you will be given a choice of dates. Very little will be affected. This is not like an OS restore. But just to be clear 'system restore' is in control panel>backup and restore> and then at the bottom of the page you will see it. On my Vista it is listed below the options 'restore files' or 'restore computer', which of course you do not want to choose.
Easiest way to get to it is to just type 'system restore' in the search box under the 'start button'.
Assuming system restore is turned on on your system.