You (re)format partitions. The drive might be 'fine' with one 135 Gb partition and 100 Gb not allocated, but maybe it's not what you want. Tell more what disk management and partition magic say about partitions and space not allocated other than "fine". Simply because that's not what they say.
I have a WD250gig HDD running on Windows XP SP2. The amount of space on the drive is not being recognized properly by windows. Disk management/properties/partition magic all say there is only 128gigs available on it. It is not a new HDD and this problem only occured after i had deleted my partitions (I had a single 100gig and a 135gig) and tried to reformat the drive. XP is running on my 2nd HDD right now. I've tried chkdsk, partition magic and WD's diagnostic program which all said the drive was fine. Is there anything else i can try or do to get the remaining ~100gigs back? Thanks.