How Do You Uninstall Ubuntu From Windows 7?
The reason why you are no longer getting the startup options is that Windows 7 bootloader have overwritten the linux GRUB bootloader. I have not dual booted both the OS yet, but I think it will be safe to format the partition containing Ubuntu from Windows 7. Ubuntu will be gone, but some leftover bootloader files may reside in the boot partition on your hard disk. Normally, different OSes cannot be installed on the same partition, so, formatting the partition containing ubuntu will have zero effect on windows 7.