I have a 11 yr old self-assembled desktop at home running Xp with 2GB RAM. The CPU usage is almost never >40%. Only used for trading and browsing (Chrome). Hence a little attached to it
I could also run algos on it if I really wanted to but I usually do that on the laptop. Never really saw the point of a high end system for manual trading.
Things replaced so far. Power Supply/UPS, CPU fan, CMOS battery plus an extra system fan. Also ethernet card.
Oh and it's a P4!