1) a reg cleaner usually casues more problems than it solves.  IF you
choose to use one, you should ALWAYS satisfy yourself that the supposed
problem is really an error, and only permit the tool to "correct" the
problem with your consent.  NEVER let it automatically fix everything it
finds, that's sure to cause problems!

2) if you're having "performance problems", that can be due to many many
things.  A trusted "expert" could probably sit at your machine and make
suggestions, but to blithly give out "advice" without examining your
specific machine would be unproductive. Your best bet would be to 1) find
a trusted expert, or 2) become one yourself.

Search around, there are sites out there that have good info on how to
solve performance issues.  Most are related to unnecessary Services that
are running, unnecessary Startup Processes, poor system settings, or poor
organization.  And of course MalWare can often be the cause, if you do not
"surf safely".

Take small steps.  There is no magic solution, just perseverance.  Good
Luck.

For a good start w/ a vast compendium of info, try the elder geek:

http://www.theeldergeek.com/