If you're on Windows 2000, System Restore isn't an option open to you anyway.
What service Pack are you up to? MS has just release SP4 for Win2K. So that ought to be amonst the first things you try.
But otherwise... Clearly the Clipboard is working or you couldn't make Ctrl/C work at all. Do you have a Clipboard Viewer? MS have a download you can get to allow you to see what's on the clipboard.
At least then you would be able to see whether it's the first Ctrl/C that didn't work or the first Ctrl/V. At the moment there is no way of being sure.