No, it's 64bit Windows 7 and no graphics remapping or onboard graphics.
The 2.75 GB (actually 2882560 KB) thing crops up in loads of old queries with no real solution, probably because the answer is to go and get a matching set of DIMMs. I don't know why it's that exact amount but I wouldn't be surprised to find it was a quirk of the Award BIOS from a few years back.
Two of the DIMMs have the same chips even though they look different: Samsung K4D5108320-UCCC. Can't find an exact match on the web, but Samsung's charts suggest it's SGRAM (???) 3.3V. Another is Hynix and actually meets the spec. The other DIMM also meets the spec but the timing is different from the Hynix.
It's a pity really, I haven't done much mucking about with hardware for a year or two and I was quite enjoying it. I suppose I was a bit naive to expect I'd get 4 DIMMs with a fighting chance of working together. I'm not even convinced they are all DDR400.
EDITED: 4 May 2015 22:07 by WILLIAMA