Yea, fairly easy to fit....
Should be no problem at all.
Though it is possible to fit a `standard` 40pin 3.5" HD in there. (there maybe an unsightly bulge)..(you need a floppy power extension cable and 44-->40 IDE cable)
My advanced tip for today:
if you notice after a soft-reset the hard drive is no longer recognised; then cut pin 1 on the IDE cable (usually the one with the stripe, and theres a `number` on the Mobo/Hd), careful not to cut any other cable wire...
This disconnects the reset signal...
This will probably not affect any modern 2.5" HD...
