Bigger hard disk on Toshiba 4010CDT

Does anybody know how to get a Toshiba 4010CDT to accept a larger hard disk. It comes with 4 GB but when I want to work with three operating systems (MSDOS; modern Windows and LINUX) this will be a problem if I also want to include applications! Conversely, I am satisfied with the computer otherwise, although it is somewhat older by now, and would like to upgrade instead of retiring it or maintaining two Laptops in order to have space for the bigger operating systems. I did look at Toshiba's site but found nothing except some information that such support is NOT provided by them! They suggest an alternative company but this company does not show any sign of supporting my model. I also would be happier to find a way to alter the BIOS and buy a HDD locally, though I did find one company offering hard disks which they suggest will work with the 4010CDT, while giving no clue that they in some way deal with the BIOS problem. (In any case, it would mean importing the HDD, with a bunch of associated problems, especially if something goes wrong. I have my fill of that trouble!) Thanks to anyone able to help. Bob