System Restore Mal-Function

Hi:

I have a Dell Dimension 4600, 3.25 GIGS RAM (as recognized by Windows XP-SP3) CPU = 2.4 GHz
2 HD's:

C: drive = total 465 Gb's, remaining = 3.3 GB's
F: drive = Total 189, remaining = 21 Gb's)

Problem:
System Restore will not, while in Windows XP, restore to any  earlier time, in spite of the following:

1) Antiviral Scan with Norton AV (2010) - negative findings
2) Scan with Windows Defener & Microsoft's Malicious Software  Removal Tool v3.11 - negative findings.
3) Webroot's Spy Sweeper - negative findings

4) Turning off System Restore, rebooting, then re-booting and
turning on System restore again, choosing a restore point and
trying again to restore to earlier point - Again no success

5) Copying the rstrui.exe file from the i386 folder to the
   Windows system32\restore file (after renaming the original
   rstrui.exe file, and again trying system restore to a
   previous time--no success.

The ONLY method that has worked is using Safe Mode.

Question:
Is this the only way, from now on, to use System Restore?
Doesn't the need for using Safe Mode point to something
wrong (corruption?) with the OS & files, etc, and can this
be corrected other than by Windows In-Place repair or clean
re-install??

Thanks for any help.