Programs Closing Can't Be Found

when running several programs on my Dell Inspiron laptop (Windows 7).

1)Outlook keeps stopping, Windows says it's checking for problems and can't find any.
2)Can't open the volume control and I have no sound lthough when I hover over the small icon on the lower right of the computer it says its at 52%
3)Can't open Windows Movie Maker from the start menu or from locating the .exe file within the C: drive.

probably others I haven't encountered today.Running Windows 7 (64 bit) on a Dell Inspiron 1545, have had it over a year. Using Avira AntiVir personal, perform full scans each night. Problem began last night (5/4/11). I received a backup file for Quickbooks Pro 2011 via e-mail and tried to restore it to Quickbooks (something I do weekly). QB program would begin opening, but couldn't. After working with a great tech from Intuit we discovered the folder holding the QB data files was the problem (corrupted?) and worked around the problem by creating a folder on the desktop to use for data and backups.Steps I've taken so far:

1) Updated MalWarebytes AntiMalware and ran a full scan. No malicious software found.
2) Ran the defrag program. C: had 3% (if I remember right) fragmented, and it ran 5 passes to fix that.
3) Updated CCleaner and ran the cleaner to delete unneeded files.
5) Avira had run last night and found nothing, so I didn't run it again.
6) In looking at Task Manager there's a file that seems out of place: qbw32.exe *32 Quickbooks isn't open and the usual QB program file is just qbw32.exe without the *32, so maybe that's a clue.
7) Another possible clue: our other computer has slowed to a crawl..currently on its 16th hour running a malwarebytes scan. Both access the same verizon e-mail so maybe something came through e-mail to plague us.