You will find RAM ($30? -guestimate) and hard drives ($75-100) for them anywhere, but be careful not to get a hard drive that is not supported by the BIOS. If the Compaq is very old it could have an 8GB limit. To replace the processor would be a difficult task and you would get only a minute speed increase. If the system does not have a cd-rom, you may still be able to find a parallel-port or PCMCIA cd-rom drive, but be prepared to spend a fair amount on it. The cheapest I found on pricewatch is $65.
If you can find out the models they are offering, post them and we will see what we can find.
hardware
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