I need to get rid of a computer that I've had for a while, I dont exactly want to part it out on ebay so I was wondering if anyones been able to sell a full desktop on another web-site.. The problem is I have custom wiring in there so if I part it out the case and psu become somewhat wasted. Any suggestions anyone?

So I need used computers every day, and can sell everything I can get. The price has to be adjusted for the failures that will occur, as well as the performance compared to new.
Where we work and run our shops, the best place is through a tech. Tech's alwasy have clients with failed computers for which they need replacements. Of course, they must make a living. Another good place is the local shopper newspaper, and the regional newspaper want ads.
College and dormitory bulletin boards.
Cable internet providers. Trailer parks. Apartment complexes.

What is important is thinking about what you have to sell - compared with what buyers want to spend... and sell the ideas as to why yours is better, or worth the extra money. Help that mother or grandmother know she is buying something her daughter will be proud to own.

Junior high kids are excellent sales possibilities. Their wants are high. They just need some time with you to understand what that unit would be a status symbol in their crowd.