As an update to yesterdays posting I got some feedback that the script I supplied couldn't be used. I'm not sure what the problem was but the safest option is just to enter the key manually. A slow performing Windows machine can of course be caused by other issues than the one I highlighted yesterday which got me thinking about a tool I run quite regularly -- CCleaner.
CCleaner will scour your hard disk for temporary files that can be deleted as well as allowing you to remove private data such as browsing histories etc. It also has an option that scans the registry for what it calls Issues and then attempts to fix them.
I tend to run it about once a month and it tends to remove about 200Mb of files and about 50 registry issues. Note that the it's worth running the Issues scanner multiple times until it tells you that it can't find anything else to fix. This is because sometimes the fixes it applies on the first pass highlight further problems.