1. Clean up registry (this will rremove registry errors)
2. Defragment registry (this will reduce the size of the registry by removing gaps from step 1)
3. Clean disks (Auslogics can do it, CCleaner can also do it)
4. Defragment disks – this is the most important step besides step 1.

After that your PC should work a bit faster, or a lot faster if this is an old computer.

@ garbanzo – Revo is good, but sometimes not even the full scan is able to find everything, and you have to do manual cleaning. I wouldn’t recommend using Revo for aplications with kernel drivers, removing those without reboot will instantly produce BSOD.
It is also not true that software only writes to HKEY_CURRENT_USER\Software and HKEY_LOCAL_MACHINE\SOFTWARE, software with dedicated drivers also writes in the Control keys, like HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001.

@ Transcontinental – indeed Russinovich doesn’t take Registry cleaners in high consideration but he also states that “Registry junk is a Windows fact of life and that Registry cleaners will continue to have a place in the anal-sysadmin’s tool chest, at least until we’re all running .NET applications”.
But yes, I also think it’s a mistake to think it will improve performance. Personally I use it only to remove clutter and sometimes to fix errors. When I need it, not on a regular schedule.

Argente Registry Cleaner – CCleaner – jv16 PowerTools – Uniblue Registry Booster 2(the only shareware) – Wise Registry Cleaner

Now, concerning Comodo Registry Cleaner, hard to know if it would add any extra potential but, in regard of Comodo’s reputation of quality, I guess I’ll give it a try, though beta stages when applied to sensitive matters as the Registry, do frighten me a bit.

As for cleaning and optimizing in general – as was said above, I think it does little good, but go it occasionally.

Better use more often defragmenter and PageDefrag.

i too use registry cleaners on occasion. i usually only manually remove keys in HKEY_CURRENT_USER\Software and HKEY_LOCAL_MACHINE\SOFTWARE, since uninstallers and registry cleaners often leave things behind in those areas. it’s too tedious to mess with HKEY_CLASSES_ROOT to clean up file types and such, so that’s where cleaners sometimes come in handy. oh, and for clearing those pesky MRU lists. cleaners use algorithms; i do not :)

not that clearing those things actually makes my computer work any better – it’s just a compulsion i have, i like my computer to stay tidy, and don’t like anything to take up space if i’m not using it…

Sometimes an uninstaller fails too, so you have to manually delete program folders. Is nice to not have to search a registry manually to delete keys that are never going to be useful again.

I like eusing free reg cleaner, even if it’s nagware, but Comodo firewall rocks my socks. I may have to check this one out then just because.

Edit: WHOA. 9 mb installer? Does it also process photos? I’ll wait to see what it’s all about I think heh.

Disproved by who?

Registry cleaners does not really improve performance but benefit of removing broken entries to such things as missing uninstallers or file associations is more than obvious.

I only use jv16, registrar (for manual cleaning), erunt and ntregopt.