If you delete the partition (provided it's on the same drive) without reinstalling the Windows Boot Loader MBR code, you will
not be able to boot back into Windows, as GRUB will be missing. If you've already deleted the Linux partitions and cannot seem to boot, insert your Windows 7 disk and enter Recovery Mode. Open a Command Prompt. I think the command is "BootRec.exe /fixboot" or something of the sort, if I'm wrong, there should be tutorials somewhere on the internet. If you can boot into Windows, install
EasyBCD. After you get it running and have already selected the BCD Store to edit, click on "BCD Deployment", select "Install Windows Vista/7 bootloader to the MBR" and click "Write MBR."