This is about the Emachine ET133G-03W with the ECS MCP61PM-GM Mainboard. You can upgrade to the AMD II X4 605e, 615e, or 620e with no problem. You can find the AMD Athlon II x4 605E CPUs at Tigerdirect.com web site below. This is a 45 watt chip and will replace the Athlon II x2 235E CPU on the ECS MC61PM-GM Ver 2.1 motherboard. You don't need to upgrade the BIOS because there is not one for this motherboard. Also can change out the 2 one gig ram chips and replace them with 2 two gig chips this will bring it up to eight gigs. Also if you add a above video card change the power supply up to 550 watts or higher. After I made the changes to mine this machine runs very fast on Windows 7 64 bit system and I haven't had any problems.
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=5315075&CatId=4919
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=5315075&CatId=4919