@Boo: First of all, what kind of Dell? The model number should be visible somewhere on the exterior of the case, and knowing it would help a great deal in terms of narrowing down what kind of hardware is already inside--the existing motherboard will affect what kinds of RAM/graphics cards/etc. you can stuff in.
Secondly, if there's an administrator password in place (I'm assuming that you're talking about a Windows and not a BIOS password), your father-in-law did not completely wipe the comp. If you have whatever system restore discs Dell provided with the machine, you might consider wiping it really completely (that is, reformatting the hard drive and reinstalling the OS). Don't try this if you don't have the restore media, however. (That also assumes that there are restore media, since some manufacturers have gotten lazy these days and ship with the restore stuff in a separate partition on the hard drive.)
@PSZ: I'm afraid not. From the looks of it, Ramsus is more knowledgeable than I am anyway.