Yes ..... and no ....
Most things can be hacked .....
it depends on which machine you have and how popular it is
I have a gizmo called a Thompson Tivo .... and there is plenty of support for this type of machine
(I now have 2x 200Gb drive giving 360 hours of recording time (at low quality) in mine ... i wouldn't be without it
Sky+ also gets lots of attention
http://www.xtendedplay.co.uk/sky-hard-drive-up grade-kit-250gb-prodid-5.html
(I know this isn't your model ... but look at the instructions - they are typical of what's involved)
You also need to understand that doing so will void any warranty.
any Upgrade depend on being able to port the operating system to the new disc - in my case this was done using an old pc and a downloaded utility ....
it was fiddly - but not difficult ... and took about 5 hours in total