http://www.projectorcentral.com/Lenovo-C500.htm
http://www5.pc.ibm.com/uk/products.nsf/$wwwPartNumLookup/_41U3038?OpenDocument
There are better projectors out there, but this is not unlike a good machine that was around 4 or 5 years ago, so may be a good start for you. You can get a 1280 x 720 DLP or LCD home cinema projector for around the same price that this model goes for on ebay, so you may want to consider selling it on. You can try it and see what you think of it before you do that though just in case you find it perfectly adequate for your needs.
It's very bright so unless you're going to be using a huge screen, you may need an ND2 or ND4 filter to dim it down a bit. It's also quite noisy by todays standards.
Gary