Hey, I own Acer Veriton M680G, Which is 64bit-4Gb RAM. It has 1 x PCI Express® 2.0 x16 slot. Ill provide the links to the detail of the computer below. Thanks a ton!
1) http://static.acer.com/up/Resource/Acer/Docs/AU-NZ/Desktop/20110225/M680%20TSS%201.2.pdf
2)https://www.cnet.com/products/acer-veriton-m680g-udi5650c-core-i5-650-3-2-ghz-4-gb-500-gb-english/specs/
1) http://static.acer.com/up/Resource/Acer/Docs/AU-NZ/Desktop/20110225/M680%20TSS%201.2.pdf
2)https://www.cnet.com/products/acer-veriton-m680g-udi5650c-core-i5-650-3-2-ghz-4-gb-500-gb-english/specs/