OK I've worked it out. I've killed a stick of RAM, and a couple of DIMM slots on my board.
So thats whay the 2 sticks don't work in the ASUS, and...
I think I've confused things with the amount of PC's I've mentioned.
I have my own working Pc, which has the OCZ 2gb.
The new ASUS.
The old Dell....
I recently purchased one of these http://www.overclockers.co.uk/showproduct.php?prodid=FS-063-AS
An Asus V3-P5G43 Barebones system
Separate names with a comma.