NO!
If you are thinking of mixing older parts(from old 1990's) with some newer ones (present 2010-2011) then it will not match.
Because over the years, the socket for intel motherboard has rapidly gone a big change.
Also with it other parts form factor have change, like for example RAM.
So, the basic answer is NO!.
But you can use some old parts in new ones like:
CD Rom Drive
Harddisk
Monitor
PCI cards (modem)
Cabinet (but depends)
Floppy Drive (if you think it is needed this days)