Just bought a computer off a friend for cheap, but it's missing the side panel. I don't wanna buy a new case, so what would be the best course of action? Duct taping on some cardboard perhaps?
Unless you have pets or kids, there really is nothing *wrong* with leaving the panel off. Conversely, you could cover it with saran wrap or the cardboard as you suggested. Anything more intense that that, however, you'd be better off just getting a new case. You can get one pretty cheap
Either call the company and see if you can get a new panel or just buy a new case. It really isnt worth much trouble considering you can get a lot of nice cases for not very much.
Go to freecycle and see if anyone is giving away a free PC or a broken PC. I have a garage filled with PC cases. If I have a panel that fits yours I'll send it to you at cost. Shoot me the model and size.