To create a restore point or restore your machine to an earlier point go to:
Start > All programs > Accessories > System tools > System restore
From here you have 2 options:
1. Restore my computer to an earlier time
2. Create a restore point
If you choose "Restore my computer to an earlier time", a calendar will appear with all availabe restore dates in
BOLD. You could then choose one closest to
BUT BEFORE the date you started having problems.
If you decide to try this, I would choose option 2 "Create a restore point" FIRST. That way you can get back to the state your machine is in right now (right or wrong) if you want to.
I've done a system restore twice.
Once because when I was gone, the "check your desktop for unused icons" utility popped up and my wife said "Yes remove unused icons"… Silly her

… The restore got all the icons back. I've since turned that off so it won't happen again.
The other time was when I installed some software (incorrectly I think because of poor instructions supplied with the software) that did registry modifications.
I'm going to have to get help on the repair/reinstall because I've not done that, and I've seen conflicting instructions on how to do that. I'm not sure which is best.
Unfortunately it's entirely possible that even after trying a "restore" and/or "repair/reinstall" you still might have problems. I say this because we still have no clue as to the exact source of the problem.
and checked the box for IE to check if it's the default browser
Hmmm… I DON'T have that box checked in my IE settings….