parts that are original to it:
-chassis
-one of the HDDs
-motherboard
-CPU
-part of the CPU cooler (heatsink)

from other computers or new:
-RAM (new, 512MB PC133!)
-PSU (pulled from another computer)
-Sound card (received from friend, nice AWE32)
-Video card (purchased on eBay, was new in-box)
-part of the CPU cooler (fan, original one failed)