Windows (XP) Registry

I receive the following notice every time windows loads after
turning my pc on daily (for the past week or more).

"One of the files containing the system’s Registry data
had to be recovered by use of a log or alternative copy.
The recovery was successful."

I’ve read others who’ve had this issue before, but I’ve
never read where someone actually gave advice for how
to resolve this issue.

Does anyone have any idea how I may begin to track
down what file(s) may be causing this, perhaps a way
to review the log itself and determine what’s creating
this issue?

One side-note. I believe the problem began a few days
(therefore a few startups) after I used a program called
"Eusing Free Registry Cleaner". It’s a free version,
which finds problems in a registry and cleans it up.
I thought about using the old registry I
backed-up, but I’m afraid I may create
more problems since I’m pretty active
on my pc, and have created text files
and downloaded photos and other things
since that time. I wouldn’t want to lose any
data. I have downloaded "Registry
mechanic" also, used it once, that didn’t
clear the problem, although I didn’t really
think it would. So my question is, how to
trace the cause of the file or files
creating this issue?

Basically for overall PC maintenance & optimization.
Which is the best for free version:
And which is the best for a paid version?
What do you think of this software called ‘PC Optimizer Pro’?

PC Optimizer Pro

I formerly had PC Tools' Spyware Doctor and Registry Mechanic, but the license has expired on those two and they no longer offer a discount price for getting both programs.

Can you steer me towards something equally good that I should look into getting? I'm looking for protection from spyware, malware, etc.

I'm not locked into getting a Registry cleaner, but would like to.

BTW, I use AVG's updated free version, so I feel I'm covered on the anti-virus front.

Any useful suggestions very much appreciated. Thanks.