Hi there,
I have a problem with my PC running Windows XP. There is a piece of malware on it that has prevented me from accessing my Outlook mail. I have solved the problem temporarily before by doing a system restore to 10th December, but eventually the malware comes back and I can't access Outlook again (Outlook opens fine, but there are no mail accounts set up).

I have since found out how to remove the malware, but now I can't restore my PC to a date prior to beginning of January this year and so still can't access my email even though the malware is now removed. For reference the malware in question is SpamBlockerUtility. It is not possible to roll back the months using the back arrow in the calendar. Does it auto-archive the previous year?? If so, how do I get at it?

No, if the restore point is not there it may have been overwritten as restore points can take up to 12% of your hard drive space and if restore points reach that 12%, the oldest one is overwritten.

What you can do is try a repair installation - no data will be lost

Repair Installation
A Repair Install will replace the system files with the files on the XP CD used for the Repair Install. It will leave your applications and settings intact, but Windows updates will need to be reapplied.

A Repair Install will replace files altered by adware and malware, but will not fix an adware, malware problem.
Perform a Repair Installation

This may help you solve your problem download and install malwarebytes antimalware and run it under normal mode and then later boot into safemode and run it then do your restore and do the same process over again and once you get rid of it delete all system restore files and create a new one