Changing the IDE cable won't do jack. Feel free to try (having extra parts lying around doesn't hurt), but I don't see that affecting it. The freebie suggestion I'd try first is to grab the .inf driver for the 915/925X with ICH6R chipsets...basically it's the most important set of chips on your motherboard, aside from the CPU. You can get them off Intel's website, and probably Dell's too. After you install them and reboot, go ahead and try my previous suggestion and see if you're okay then.

If not, you might try getting this IDE controller card. I'm almost positive its the same thing I have in my main box, and it works fine for me with optical drives. I can't say for 100% sure it will fix your problem, but I will say I don't have problems with my CD-RW drive when burning.