XP SP3 System Restore cannot be started - Access is denied

I have read the replies to DaveWWW's question on this subject written in June 2010, but it hasn't helped.

I am running XP Home SP3, and had to reinstall SP2 and then upgrade to SP3 because I couldn't get round a BSOD (0x0000007B error). PC is now running ok, but I can't get System Restore to run.

Symptoms are :-
a) No System Restore tab in System Properties
b) can't start the System Restore Service - "Could not start the System Restore Service on Local Computer. Error 5: Access is denied"
c) running System Restore in System Tools fails - "System Restore is not able to protect your computer. Please restart your computer, and then run System Restore again"

I've scanned for viruses/spyware using Norton Internet Security, MalwareBytes and SuperAntiSpyware

I've tried reinstalling sr.inf using the "rundll32.exe advpack.dll,LaunchINFSection c:\windows\inf\sr.inf" run command (using the c:\windows\ServicePackFiles\i386 folder when prompted for source files)

I've tried deleting the 3 files from c:\windows\system32\restore  prior to doing a sr.inf reinstall

I've also tried doing all the above in Safe Mode

The System Volume Information folder is "owned" by the Adminstrator

Any ideas please?
Thanks
Geoff