Description eMachines EL1200 - 06W
•AMD Athlon 64 2650e Desktop Processor
•1GB DDR2 Memory
•160GB 7200rpm SATA Hard Drive
•18x DVD+/-RW Dual Layer Burner With LabelFlash Support
•NVIDIA GeForce 6150SE Integrated Graphics and eMachines E19T6W 19-inch LCD Monitor
•Integrated 7.1 Audio With Stereo Speakers
•v.92 56Kbps Modem, Gigabit Ethernet
•Seven USB 2.0, 14-in-1 Card Reader
•10.7" x 4.2" x 15"
•Windows XP Home, Works, NTI DVD Maker, Norton 360
Having looked at a few photos of this newish compact model, I'd think you can add any standard 3.5" SATA II drive if you firdt remove the optical drive. Western Digital 500GB Caviar Green would be a good choice on a 220W supply.http://www.westerndigital.com/en/products/products.asp?driveid=338
I don't know what issues you will have transferring the OS over, but the free download of Windows 7 RC1 would be fun to try. You can also add a dual core AMD4050e and up to 2X 2GB of DDR2-800 memory by the look of it.