Where are you? Did you try using the internet and asking that way?

Well if you're disabled, you probably get money from the government, so I would suggest, if at all possible, to put aside a bit of money every month or week, and attempt to save up for one. In the meanwhile, you can do your research, either in public internet places or fliers and whatnot, to find what you want. You can also head to individual businesses, they can usually put together a damn decent computer for you, for nearly half the price of a new one.

Check around your location for "computer recycling" organizations. One location in Kansas City, Missouri, called "SurplusExchange", sells computers fairly cheaply: right now they have 2.4Ghz PCs (think about four years old, but still fast enough for modern applications) for between $20 to $65, and $10 monitors, $2 keyboards, and $1 mice. Since LCD computer monitors became the rage, CRT monitors (the ones that look like older television sets) have become quite cheap, with even 19" models dipping below $40 in price for used monitors. Local charities often have programs helping low-income and disabled people get computers, since they can sometimes help low-income people rise higher in income and disabled people socialize more with others. If the charity you call has no such program, chances are they know a charity which does do this. Finally, you could always place an ad in Craigslist requesting someone's older computer, and mentioning that you are disabled may bring in many offers. I have answered some of those ads myself with computers I rebuilt for the disabled, so there are people out there who can help. Personally I would recommend not going below 1.6Ghz for the computer's processor on any donated system, as I have a 1Ghz system which is not fun to use, and two 1.6Ghz systems which are fast enough to be enjoyable to use.