Take it from a computer tech that thinks he knows a little.. Your windows registry file is a database of settings similar to a access database for arguments sake. The whole thing is broken up in several sections and the most important 2 is the software and system settings. These two files are generally around 20-60Mb combined. Loading all those settings into the memory would take even a VERY slow hard drive only 1-2 seconds. So the physical size of your registry does not impact performance at all, the whole concept of "cleaning" the registry is utter BS. Next up is what the registry actually does, there is about 900 million settings in there for how windows and programs behave, lots of "make my computer uber fast" programs just change visual settings like how fast windows pop up and if they fade in and out etc to give you the false impression of a faster computer. Some try and search for "dead/unused" settings in the registry which brings me back to my first point. They take no time to load, they use almost no memory so why would deleting those keys give you any benefit? Conclusion: Registry cleaners = snake oil/bullpoop Want to make your old computer faster? Get a hirens boot cd and scan your hard drive for UNC's with mhdd or vivard. If you have no unc's (if you have <10 remap them with the same program) do a defrag with mydefrag. Use autoruns to disable the 700 startup entries that you dont need. Uninstall the 75 toolbars that you have picked up over the years for IE/explorer. Not helping? format and reinstall is the only way.