If you figure out you don't need Ubuntu anymore, you might want to uninstall it from your multiboot config. Please note that the following assumes you have Windows Vista or 7. Step 1. Boot into Windows. Open the start menu and in the search box type "computer management". Once in the mmc (Microsoft management console) look for the disk management tool. Step 2. Delete/format your ubuntu partition. WARNING: DO NOT REBOOT OR ELSE YOUR PC WILL BE RENDERED USELESS. Step 3.0. If you don't have a Windows vista or 7 disc, google 'Windows 7 digitalriver' or 'windows vista digitalriver.' Or if you want use torrents. Find and download the iso. Burn the iso to disc (don't burn the iso file to disc. If you have windows 7 then double click the iso image to open it in the windows disc burner otherwise use something like PowerISO). If you have a windows disc then skip this. Step 3.1. Insert your windows disc (or newly burned disc) into your disc drive and reboot. At the press key to boot disc, press a key. The windows disc will load. Step 4. At the startup page, go to the repair your computer bit and go to command prompt. Step 5. In the console, issue this command: bootrec /fixboot And let it complete. It will tell you once done. Step 6. Issue: bootrec /fixmbr And as stated above it will tell you when done. Step 7. Exit the command prompt and windows setup. (Ie reboot) and you will boot in windows. If you see a boot menu, choose windows NOT ubuntu. Tada da da-dum! You have deleted ubuntu. :sigh: using closed sourced software again. ------------ What happened behind the scenes. You delete ubuntu, which also deletes GRUB's most important files but leaves the grub recovery in the Master boot record (mbr) (grub replaced bootmgr, 7/vistas boot loader when you installed ubuntu). Without grubs important bits, your computer boots into grubs recovery thing, so you boot into the windows install disc. You then fix the boot loader with Fixboot and fix your MBR with fixmbr.
Edit to step 1: look for and OPEN disk management. Don't just look at it and then expect ubuntu to delete itself