Your disk may have a jumper to let it announce 32GB, as this was useful with the hated Award 4.51pg Bios. Fat32 would be another explanation.
Heath: use ShDiaghttp://www.samsung.com/Products/HardDiskDrive/utilities/shdiag.htm
read and follow the instructions. Create a Cd, boot from it.
A 80GB disk isn't the fastest now and may lead to disappointments with Seven.
For further discussion, the disk model (especially if Pata, Sata...), the mobo model and Bios settings (Ahci?) would be useful.