Originally Posted by andrewthomas
To remove your Ubuntu install, you should boot to your Ubuntu LiveCD and delete the partitions ( /, swap and /home if you have one,) then you will need to restore the windows bootloader to the MBR.
I don't think there is any good reason to do those things in that sequence. The opposite sequence gives you a much better chance to find a work around if something goes wrong.
1) Follow those instructions andrewthomas linked to get and use a bootable recovery CD to give control of the MBR boot code back to Windows 7. There might be ways to retake the MBR from inside the Windows system and not need a bootable CD, but I don't know where to find those instructions. (If you do find the way to fixmbr from inside the Windows system, you obviously need to do that step before deleting Grub).
After that works (and Windows boots directly without Grub).
2) Use the partition manager in a bootable Linux CD to delete the Linux partition(s). That might not really be necessary, because the partition manager in Windows also can delete foreign partitions.
3) Use the partition manager inside the Windows system to grow the Windows partition and/or create a Windows data partition to use the space freed by deleting Linux.