No. you can buy used ram; I like to purchase ram locally off craigslist, but ebay is fine. Any variety of non ecc crucial ddr2 that matches your current ram speed should work fine. I also use gskill, patriot, corsair, and kingston. But for best results, pull a stick and google the ram model number and try to match it exactly. Check dell specs and be sure 2 gb sticks will work. 4 gb is normally plenty; I've found some used 2x2 gb kits for around $40 on craigslist. You may also run memtest (a free download) with each stick one at a time in the ram slot closest to the cpu. If your ram passes memtest, then the problem may be in the board, not the ram. Older boards sometimes have capacitors that go bad; then I would replace the board.
I'm actually going to replace all of my RAM (which is in a 1x1 set up with 4 separate sticks) in trade for the 2x2 setup. My mobo supports 2x2 and a max speed of 800MHz
I just wasn't sure if the ones I want would work or not.