Well, if he doesn't want to do much more scanning then with protein gels or electrophoresis, or any protein analysis that is, he don't need a powerfull pc with a nice screen.
What he need, basically, is something to run an image editing software to play with the contrasts of the image. The gimp would do the job and it's free.
He need a screen with good to high contrast and color accuracy isn't important to him. An entry level lcd or a 17 inches crt would be enough.
He don't need raid or a huge hd since he won't be analysing thousands of gels each week... it takes a while for HPLC. It's not like if he was shooting 1 of 2 GB of photo each day...
He need a graphic card for 2D editing. a matro g450 is enough.
He need ram for graphic editing and here i'd say 512MB is enough. Just get some quality brand for stability need.
He might want to install linux since unix is quite used in research labs. All of his software would be free...
Any flatbed scanner would do the job
FOr everything else, get what you want. The average hardware is enough and will do the job for YEARS.
i hope this helps
mufff