Starmicro has several 400 fsb socket 478 cpus; I would recommend the 2.2 for $11 plus shipping. If it doesn't work, you're only out about $17. But I also recommend a new motherboard, cpu, and memory. Fry's has a celeron 430 with board for only $59.99 (may include heatsink, depends on fry's location). Ddr2 starts at about $20 per gig; 2x2gb kits go for $20-40 after rebate. Check your case to see if the board is micro atx with a removable backplate; if the backplate is fixed to the board or with rounded corners, time for a new system. You may also upgrade the memory to 2 512 sticks of pc133, but it probably costs alot more than ddr2. I found my complete compaq pc for $199 last may at Fry's anniversary sale.