Build a server with all the drives you have, put it in the basement, connect it to the HTPC via wired gigabit network, and you should be access your movies instantly from either WMC or XBMC. Plus, as you add more HTPCs to other rooms in the house, they will be able to access your digital colleciton through the network too.
Edit. Use a server software that will allow you to create redundancy without having to delete the drives, so that when you lose one drive, you won't have to re-rip/re-download them again.
We have about 1500 movie titles, and I sure as heck would hate to have to re-do it all. We started the server when the DVD count reached 20 or so back in the 90's. It was just too cumbersome to look for a DVD to put in the player when you wanted to watch something...
Still running the same server on PII 233 MHz with MMX, just using a different RAID controller.
6 TV's in the house on FiOS and we only pay $4.99/month to connect them all!!! Power to the CableCard and WMC7!!!