At the risk of causing information overload...
Those things that "could not be found" may have been aliases. That term refers to an icon that is a copy of the original icon of a file or program, and will open the original when you click on it. It's a quick way to get to things that may be buried deep in your folder hierarchy. In fact, Windows users call them "shortcuts".
Typcially, a Mac alias name will be in italics. When created, the Mac automatically appends the word alias to the name, but the user can remove it, and in fact rename the whole thing to something else. So, if the previous owner left a bunch of aliases on the computer, but wiped off the originals, clicking on them will produce an error message like the one you reported.
To make matters worse, an alias name might not be in italics. The user can set that in the computer's preferences. (gang, is that in the finder prefs? - I'm on lunch break at work) So, one way to find out if an icon is an alias is to highlight it (single click) and Get Info (from the edit menu, I think) and see if the Info mentions alias. If it does, and clicking on it gives you that message, you can safely drag it to the trash and never worry about it again.
