There are many options available for external Hard drives. I use USB 2.0 external hard drive case from ADS, (with 120 Gb Western Digital HD). I also have an 80 GB Firewire hard drive. Both are dedicated to Video capture, (the USB 2 for my laptop, and both are excellent. The USB 2 drive benchmarks a little faster, though I haven't experienced dropped frames with either.
Hope this helps some. (Unfortunately, I have no experience with Xtradisk).
JTH

I don't know about XtraDisk. As with most computer stuff I buy, I purchased my external drives just before (or just as) the external 'cases' that allow you to use internal drives externally appeared.

On the other hand, I now have (and have had) my drives to use, and, although the boxes might allow for a bit more flexibility, my drives work just fine. I have three 80GB Maxtor firewire drives. They only spin at 5400 rpm, but I use them for video all the time without dropped frames or other problems.

The salesman at BB where I purchased one of these drives told me that if ever I wanted a faster drive, opening the case and sticking any IDE internal drive into it would be no problem (warnings in the instructions are ominous, like the tags they put on pillows and sofa cushions (must not be removed under penalty of law).

Anyhow, I'm happy with my external storage options for now.

Good luck.

Caruso

Like this other gentleman said earlier: Promise Ultra 100 TX-2 card.

This is a PCI-slot additionnal IDE ports card that will cost a fraction of the external FireWire solution and will give you a possibility of 4 more drives, ATA 100. I use this and it's flawless with 4 x 80Go drives (Maxtor and Seagate)
A note here: be sure you have enough space inside your tower to install all those drives plus check your power requirements (you may have to change your power supply...)

Otherwise, consider comparing prices between these two options:
-An already "built" ext FireWire drive (Maxtor, LaCie, etc...)(by the way, LaCie actually uses Maxtor drives inside...)
-A FireWire casing that will accept a hard drive plus (indeed) the cost of the hard drive you want to install in there... ADS Tech makes those cases, among others...

I don't know about USB 2 enough to give you my opinion, never tried those...

Futz:
How much would it cost to add the PCI card you mention along with, say, one 80 GB card? You've probably shopped the Maxtor externals. Given that my machine was already firewire capable, the PCI card would have represented additional expense which would have to be offset the lower cost (or perhaps higher capacity/performance at the same cost) of the IDE drive.

How does the PCI solution compare, in your opinion, to the external firewire solution in terms of performance/cost?

Thanks.

Caruso