Unable to see the full size of my 500 gig External hard drive

I have a 500 gig My Book which works fine expect for the fact that I can only see 250 gig of the hard drive. Where has the other 250 gig gone to? What’s the solution. Don’t really want to format drive though as it would mean backing up loads of stuff and using loads of CD/DVD media. Thanks

How does it show up in Disk Management?

How did you originally partition it? Single partition? Multiple partitions?

Could we see the partition table and boot sector with Microsoft’s Sector Inspector?

Extract the above archive to the one folder and execute the SIrun.bat file. The procedure will generate a report file named SIout.txt which you can then upload to a file sharing service so that we can examine it.