Start menu - right-click on "computer" and select "manage" click on "Disk management" and... Oh, that doesn't work on my computer and presumably yours.
try GParted, it's free.
GParted -- Welcome
I reccomend just using gparted to delete the partition (and make sure there isn't some sort of "wrapper" left behind when you delete) and use the above to merge... I used Gparted to extend a disk and it changed the drive letter, making it unusable and complicated to fix.