What Virgin mean is that the disk. with all the usual useless 'stuff' on it, won't run on Win98/ME.
Sky say the same thing about theirs.
The disc is not required to set up the connection it's just bloated powerpoint 'how to' slides and sponsored AV progs. I was running NTL BB for years on a machine that was win98 1st edition with no probs at all. All your friend needs is their username and password. It may be worth checking a Virgin Media BB specific forum for exact details of setting up without the disc. I did know of an NTL one but thast was set up years ago.