ubuntu uses Ext2/3 format whihc windows doesnt recognize, you cna get progrmas for windows to let windows see the drive, but it changes systme settings so not a good idea.
to remove ubuntu is very easy(ish) in vista.
first you need to fix the MBR (it removes grub which a stanrd format doesnt touch.
1. Put the Windows Vista installation disc in the disc drive, and then start the computer.
2. Press a key when you are prompted.
3. Select a language, a time, a currency, a keyboard or an input method, and then click Next.
4. Click Repair your computer.
5. Click the operating system that you want to repair, and then click Next.
6. In the System Recovery Options dialog box, click Command Prompt.
7. Type Bootrec.exe /FixMbr, and then press ENTER.
Now you need to fix the MBR(so Grub doesnt freak out wiht linux gone)
1. Put the Windows Vista installation disc in the disc drive, and then start the computer.
2. Press a key when you are prompted.
3. Select a language, a time, a currency, a keyboard or an input method, and then click Next.
4. Click Repair your computer.
5. Click the operating system that you want to repair, and then click Next.
6. In the System Recovery Options dialog box, click Command Prompt.
7. Type Bootrec.exe /FixMbr, and then press ENTER.
( i hate copying n pasting but hey, better than mye retyping it)
then to remove the partion Start - Computer - right click - Manage - disk Mangment - either
Right clikc ubuntu partion and choose format, choose ntfs, this will give you two partions ( which can be handy)
or right click the windows partion and choose extend, and put in the size of hte ubuntu partion.