I've been thinking of using a computer case as well since a friend of mine mentioned the idea to me a few days ago. Here is a site to help our research:

http://www.highbred.net/forums/index...122&hl=pc+case

also, here our a couple of cases you could use because I dont think anything smaller would be worth the while:

http://store.yahoo.com/mypccase/atxfultowcas2.html,
http://store.ramplus.com/78qufutoatpc.html

I was actually thinking about useing two of the first case, one for a mother/clone chamber and possibly to house the ballasts, reservoir, pupms and power supply. The other would be devoted solely to flowering. Thats all I have for now, maybe soeone else can chime in with some lighting/hydro system advice.