Half of my hard drive gone?

Very simple problem complicated solution. First off I have a hp pavillion dv6700 running windows vista. I bought a new laptop awhile ago and started using it after a few months I came back to this computer but I forgot the password so I ran a system restore. Well after running the restore the computer works fine but my 220 gb c drive is now readings as a 110 gb c drive. I checked disk management to make sure there wasn't any unalloted space and there isn't. Any solutions you can come up with would be great thanks.