OK, got bored and had another go at this. Plugged the card in, nothing. Connected a monitor, nothing. Re-seated the card, nothing.
Then I looked at the SATA ports on the side of the board and thought "aha". Turns out that the two eSATA plugs were right up against the card's cooler. The card was still seated in the PCI-E slot but the SATA ports were stopping the back end of the card slotting in properly - it's an OEM Dell 7800GTX and it's a long-format PCB.
Problem solved - CUDA drivers install fine, lspci recognises the GPU
New problem is that the GPU isn't supported for folding, which was the original purpose. D'oh!
| Windows to Linux - Tips from Experience
Desktop - Galileo
Dual-Boot: Fedora 13 x64, Windows 7 x64
Intel Core2Quad Q6600 @3.6GHz, 8GB PC2-8500 DDR2, ATI HD4870, 23" @ 1920x1080 + 20" @ 1600x900 (both DVI-D), 2TB ICH10R RAID0 array, Custom Watercooling
Laptop - MacBook 5.1 ('08 Aluminium)
Dual-Boot: Fedora 13 x64, Apple OS X
Intel Core2Duo, 2GB 1066MHz DDR3, nVidia 9400M, 13" LCD @ 1280x800, 160GB SATA