This is the right place for your post.

How old is your current drive? some have 3 and 5 year warranties.

Large IDE drives are getting rarer (and pricier), especially in the 750Gb size.

I don't know of any reputable online dealers that have stock of any 750's (though there are some overseas ones on eBay).

There are quite a few 500Gb ones around though.

Beware the Western Digital Caviar Blue Drives do not work in S1 TiVo's.

I have not bought any replacement S1 drives for a while now, so unsure what else may be incompatible in the current range. Assuming you are installing only a single drive; Seagate, Hitachi (Cinemastar), and Samsung have been good in the past.

Peter.