I'm not quite sure I understand your issue. You have a 300Gb hard drive. If
the issue is that you are using a PVR and running out of space on your drive,
the solution may be as simple as changing your MCE settings to a smaller file
size in recoprding, or, instead of replacing your current hard drive with a
bigger one, if you are going to spend the money for a 750Gb hard drive, place
it as a second hard drive, dedicated for media.
Me, I have 3 - 250Gb Hard drives. My system drive, which only holds my
system, an external Firewire drive dedicated for Media (Movies and music),
and a USB drive dedicated for "anything else"
How this helps is that my system drive stays clean for the most. of the 232
Gb totally available, I have around 200 Gb after all my Vista and other
program installs. Keeps my system clean and room to expand. My two other
drives allow for back-up and safe storage. If I have to re-load Vista, I
don't lose anything that is important.
This is just one idea to help with the shrinking drives.
Hope this helps