If you're installing, trying and uninstalling lots of software, then a VM is very useful because they can be quickly reset to allow testing of new software in a "clean" environment - so there are other advantages.
As for your question:
Possibly. It depends entirely on the software.
If a piece of software uses/installs services, registry entries, background tasks, drivers, shared DLLs, etc - then yes you could potentially get performance loss. Even more so if it doesn't remove them when you uninstall the software.
But, any well written software should entirely clean up after itself when uninstalled.
Bottom Line
If the software isn't running and doesn't install any services, registry entries, background tasks, drivers, shared DLLs, etc, it will only reduce your disk space and not affect your performance (unless you're out of disk space, but then you've wider issues).
If the software installs any services, registry entries, background tasks, drivers, shared DLLs, etc (and/or leaves it behind when uninstalled), you might get performance loss. But it also might not be noticable until you've done this with lots of software, depending on how powerful your system is.
1So then, any performance hit is the fault of the software developers and not Microsoft. What do you mean by "system core", though? – Sasha Chedygov – 2010-08-25T09:53:00.983
2@music Sorry, "system core" was me being lazy and not retyping "services, registry entries, background tasks, drivers, shared DLLs, etc" from earlier in the post. And yes, I'm inclined to say fault is primarily with the software, not Mircosoft. In theory if you install then uninstall a piece of software the system should be identical to how it was before the install, this is unfortunatly often not the case. – DMA57361 – 2010-08-25T10:02:22.860
I see, so my suspicions were correct, then. Great answer, and thank you very much. :) – Sasha Chedygov – 2010-08-25T19:36:28.923
"Registry entries" in general don't slow down the system any more than files do. Really, the registry is just a file system for very small files. – Jamie Hanrahan – 2019-01-06T23:35:50.480