PLEASE can we put the old canard about IDE devices on the same channel forcing everything to operate at the speed of the slowest device to bed. Essentially all mobos made in the last 5 years support independent device timing and have no problem running an ATA-100 and an ATA-66 device on the same channel at different speeds.
ATAPI devices like optical drives use a different protocol and may slow down a fast hard drive on the same channel (but they WON'T cause it to run at ATAPI speeds!)
There's a good discussion of the matter on
http://www.storagereview.com/guide20...onfTiming.html and
http://www.storagereview.com/guide20...rformance.html
And onehunga, I wouldn't format your old HDD for a LONG TIME (like 3/12), despite the good Orac's advice - the old drive works, and if all else fails or if you stuff up your shiny new drive or installation you can always stick it back in and be sorta back in business pronto. Once you've confirmed that your new setup is working and you've transferred your data across, take out the old drive, wrap it up tenderly and put it at the back of a cupboard. If everything is tickety-boo in April then I suggest that you buy a removable hard-drive caddy and use the old drive for backup data storage (don't leave you backed up data in the same machine or even the same house).