My friend doesn't want to install anything, they want it pre-loaded. Which suppliers would you recommend?
Dell might be an option, This seems to be a good round up of what is an option.
Personally I would preload it myself as there are many different versions of Linux and Ubuntu and they are always being updated .
The load it yourself option is a good one if you want to muck around with it. I've given up on Linux for the time as there is always some piece of hardware that I have for which there is little or no support for. The lack of a decent alternative for Access is also a deal breaker for me.
I abhor PC World. But, in many towns, they're the only computer shop that there is. Good, if you need to take the machine back, for some reason.
If she has a local one-man-band kinda shop, though, that might be better.
Make sure he/she gets the installation disk, too, though, not one of those pathetic rescue disks. Just in case...