Well first...Does the Bios reconize the drive as the correct size?
If not....go in Bios and be sure LBA is enabled.
Also be sure to set bios to "auto detect"
If it was enabled, then you may have to remove the cmos battery to clear the previous settings from the other drives.
Then connect ONLY the drive in question to the primary with it set as single drive.
Upon booting it should be reconized as the true size by bios.
There are several other people having the same problem, just google search
http://www.google.com/search?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial_s&hl=en&q=maxtor+hard+drive+wrong+si ze&btnG=Google+Search
Thanks
Dudelive