I get the following when I run RKR without running anything else at the same time:

HKLM\SOFTWARE\Classes\CLSID\{3643ABC2-21BF-46B9-B230-F247DB0C6FD6}\AppId2 7/10/2006 11:52 AM 4 bytes Data mismatch between Windows API and raw hive data.

NOTES:
- It always gives the current date.
- I can delete the specific entry in the registry and a new one with a new number comes out next time.
- I have run UnhackMe and it says everything is OK.
- I have gotten rid of temporary files.

Any indications of what this may be and it if is safe would be greatly appreciated.

Thank you,
Mitsa.

I've done some research on this, and that key is strongly suggestive of malware, including a BHO, called TrojanDownloader.Win32.Small.fe. Here's a reference for it from CA:

http://www3.ca.com/securityadvisor/pest/pest.aspx?id=453075049

Since you seem to have found at least one malware on your system, and there may be more, I recommend that you start by following CastleCops' Malware Removal and Prevention procedure, a new system CastleCops devised to enable users to either partially, or fully clean their systems without the direct aid of an expert.

You will find the Malware Removal and Prevention Procedure here:

http://wiki.castlecops.com/Malware_Removal_and_Prevention:_Introduction

If that doesn't fix the problem, then go to this Forum, read the instructions at the top of the page carefully:

/f67-Hijackthis_Spyware_Viruses_Worms_Trojans_Oh_My.html

Follow these instructions:

/t102301-Hijackthis_Guidelines_Read_Before_Posting.html

and one of CC's trained 1st Responders or Security Experts will help you. If they identify a confirmed rootkit, whichever expert helps you may decide to refer you back to the RR Forum. But, first, let's let them identify and help you remove everything they can.

When you do post in the HJT Forum, please make sure you include a link to this thread so whomever helps you there has the benefit of the information from this thread.