Re: AMD Sempron 2800
If it's Socket-A, then just get a new motherboard and CPU, and make sure it's Socket-939.
If it's Socket-754, then you might be alright getting the socket-754 Athlon 64 3700+, which runs at 2.4GHz. Unfortunately, it's 130nm and only really gives a higher clock speed, but then again, it don't have SSE3.
I'd say just get a new socket-939 board with a socket-939 CPU. There's some pretty good budget boards now.
Windows XP Pro 17" LCD Monitor (1280 x 1024)
nForce3 250 Chipset Athlon 64 2800+ w/ C'n'Q
1 x 512MB DDR400 CL3 SDRAM 40GB IDE 7,200rpm HDD (8MB Cache)
nVidia GeForce MX420 64MB PCI On-Board Audio