I've used the IDE to SATA internal adapters and they usually work well, especially for optical drives. However, this was usually for the purpose of data retreival of older drives. Keep in mind that for your HDDs, you're going to be sacraficing performance because the rate is somewhere around 1.5 GB/s with any IDE adapter, instead of what your mobo can really handle (3 or 6 GB/s). That in mind, you are honestly so much better off with getting new HDDs. That are insanely cheap these days and probably run with a higher RPM than your IDE drives. Plus, you'll be able to utilize your mobo's SATA port speeds.
 
As a system builder on a tight budget, I completely sympathize with the need to reuse parts. But with this project, you'll be selling yourself short by trying to reuse IDE drives. There are so many places and sites that have sales, you'll be able to replace all of your drives for under $100. Check out DealNews.com. I get a lot of equipment through there and can vouche for it. Instead of spending around $50 to convert your IDE drives over to a SATA system, take a look into replacing the drives with SATA.

Myke: Thanks for the advice/suggestions. Here's what I ended up doing: I got the StarTech PEX2IDE card(around $20) and it does the job. I have a hard drive AND a DVD RW hooked up to them and they both work fine. Only small problem I had is that the included flat IDE cable was a bit short to fit in the case(it was an 18" cable) but I had some spare cable laying around that did the job. So for 20 bucks I got what I wanted/needed. I also notice, as you stated, that the price of the SATA drives is WAY down, it is amazing what the prices are getting to be; BUT, that said, I only have one SATA connector left on my motherboard. But again thanks for the advice/suggestions.