Can't update, won't update

I'm trying to update my copy of software x. I've uninstalled the old version of the program, but when I try to install the new one I'm told to completely uninstall the old one first. I thought I'd already done this. What's it talking about?

When you uninstall a program, despite what you are led to believe, lots of junk is left behind which can conflict with later installations of the same program. The chief concern is that the program's now redundant registry entries are left untouched and first need to be swept out before you can re-install the new version. This can be done manually using regedit.exe, but it will take a very long time to flush out every last useless entry, and even if you are very thorough, you can't be sure that you've got rid of everything.

A much more sensible solution is to delegate the task of spring cleaning your registry to a heavy duty, third party alternative program such as jv16 Power Tools. This miraculous time saver will allow you to identify all the entries associated with a particular program so that they can be removed safely. Not that this involves any effort on your part - all that is required is that you tick the relevant boxes and run through the whole suite of clean up options to ensure that an exhaustive search is conducted.