I build most of our computers so there's a whole lot of old parts floating around
Wife- (my old rig) - AMD Dual core 5000+ 4 gb DDR2 + Radeon 6850
Son - AMD Phenom II 965 + 8 gb DDR 3 + Radeon 7850
Daughter - AMD dual core 3400 + 4gb DDR2 + 5450 ( this is built on some $40 value board I bought in 2008 that's still alive lol )
Me - Phenom II 965 16 gb DDR3 + R9 280x ( I know, I know, I need to upgrade the processor )
I think I've been extremely lucky, we've had very few parts fail over the years, so I've been able to re use a lot of things.