Have i got a dud HDD? = No
Did my old pc only see 30 gig cus its too old to see 80? = yes bios may limit to 32G
What was all that unpartitioned stuff on about? = the remainder of the 80G drive.
If you have FAT32 partitions, it is much simpler than with NTFS. Just boot with a Win98 floppy and copy the NTLDR or NTDETECT.COM files from the i386 directory to the root of the C:\ drive.
Have you got the hard drive install formatted to 80g approx and win2k installed?