Registry Cleaners?

Can anybody recommend me any free registry cleaners (good ones that don’t stuff up your computer) available for download suitable for win xp?

I found 2772 invalid entries on my computer. Is that a lot?

I found CCleaner one with good feedback from users.

I have Easy Cleaner 2.0 on my Windows XP PC. Upon running the Registry cleaner, it came up with 220 invalid entries. Is it safe to delete these? Should I somehow backup my system before I delete them?