One genuine technical issue that drove traffic to this search term was a unique Windows 7/8 bug. If you uninstalled FL Studio 10 without using the official uninstaller, the registry key remained. When you tried to reinstall, the installer would see the orphaned key and assume the software was still present.

Some FL Studio 10 versions had a bug where scanning for new VST plugins would temporarily overwrite the registry key with a demo placeholder. The fix is to re-enter your RegKey and immediately set the registry key to read-only (advanced users only).