If you mean registry cleaners and optimizers we Mods don't recommend any at all because they invariably clean out more than they are supposed to and you end up with a dysfunctiional system as a result.
Windows has it's own Disk Cleanup in Control Panel (in XP I believe it's called "Free up space...." and you can help by clearing browser caches now and again and emptying the temp folders.
McAfee SecurityCenter also has "Quickclean" under PC & Home Network Tools which can help.
I have used CCleaner in the past with extreme caution to get rid of stubborn programmes that refuse to leave, but my last experience with Registry Mechanic (for example) ended up in my having to reinstall Windows....minus that software.
Winferno has a sales agreement with McAfee and they do cleaners, but I don't recommend them.
I mostly agree with what Ex_Brit has said. The reference to
too many pop ups with free cleaners
may be those Winferno-sponsored advertisements that McAfee delivers, although I've never seen one in a pop-up - they come via email, and so are easy to ignore. Winferno's registry cleaner is best avoided.
If the pop-ups are for something else, then that sounds like third-party adware is on the system.
As for cleanups on XP, the built-in programs (Disk Cleanup and IE's Delete Browsing History) do a good job in cleaning up Windows and IE8 files but won't touch, for instance, Firefox or Chrome files. That's where CCleaner has the edge. It allows you to specify whether to include or exclude files created by each of the browsers and applications on the system.
In defence of CCleaner's registry cleaner option, I sometimes use it because it's one of the very few products which allows you to be selective about which registry entries detected by the program you actually delete. Even McAfee's QuickClean just presents you with a dialog which says (x) entries found to be removed, do you want to remove them Y/N? And for the record I rarely see anything from the registry selected for removal by CCleaner, and always check to see what it is before I approve removal (knowing how to use Regedit for viewing entries helps here).
There are too many registry cleaner products on the market, and 99% of them are pure snake-oil. Microsoft techs ran various tests on the market leaders a few years ago and gave them all the thumbs-down. They didn't test CCleaner though, so I don't know what they think of it.