Is there a "free registry cleaner" that's actually free and doesn't ask for payment after the scan?

CCleaner.

A Windows Registry Cleaner that's free, easy to use and safe to use, is the Auslogics Registry Cleaner software. Just make sure to get their free software. I've been using it for a couple of years with no problems. It is safe because if you accidentally do something in the Windows Registry you shouldn't have, the next time you open the registry cleaner, you have the option to "undo" the previous cleaning.

so called registry cleaners are TOTALLY unnecessary with 2000, XP, vista and 7 they belong to the days of 98 and ME, CCleaner as with many others can make your computer unusable if you do not set the defaults exactly right, there are apparently useless registry entries and tmp files that are essential to various windows processes and security programs, defragging is in the same class modern udma 6&7 and sata II drives are so fast that the last thing the read/write heads need is contiguous data blocks, spinning at 150 revolutions a second it doesn't matter where the data is

ccleaner isn't free and it added malware right after it ran. Now they do fix 15 errors for free maybe that is what they are going for.

Yep. http://piriform.com/ccleaner does a pretty nice job for me. It is free, if you don't buy the priority support and use their download button instead.

LOVE CCCleaner!