For RAID0 you'll want the drives each on their own cable. Preferably not sharing with optical drives or anything else, though that may not be possible. Keep in mind that your PCI bus, (over which your IDE drives connect) is a hub, and all the hardware on it shares ~133MB/sec. At some point, you simply can't go any faster with that motherboard and bus.
Hmmm. A little knowledge is a dangerous thing - and you should have done some digging before you forged ahead with a senseless "upgrade".
Look, here are the facts: large hards drives are faster than small ones. By a big margin. A 400GB SATAII drive will be a heall of a lot faster IN EVERY BENCHMARK than a couple of poxy old, IDE 60GB drives in a raid array.
So, not only did you create a system drive which is slower than a decent single drive, you also used crappy old components in a system where the Mean Time Between Failure is now probably 10 times higher than when the drives were new - and twice as likely to fail as either of those drives.
Simply stated: when making RAID arrays (and let's be clear about this - anything except RAID1 and RAID5 is just stupid in a domestic setting) you start with THE VERY FASTEST HARD DRIVES AVAILABLE and IN THE LARGEST SIZES AVAILABLE and then you create your Oh-My-God-I-Just-Lost-All-My-Data RAID0 array.