At the grub rescue prompt type:
grub rescue > chainloader (hd0)+1
Hit the Enter key and then do:
grub rescue > boot
Hit the Enter key again. That will generally work if windows is loaded on the first partition of the hard drive.
What happened is that when you installed ubuntu it overwrote the windows bootloader on the mbr with grub, the linux bootloader. The configuration file for grub was on the linux partition which you deleted so grub has no clue as to the location of your windows installation. Your windows installation is still there; you just need to restore the windows bootloader by overwriting grub which is currently installed on your mbr. To do that, you generally need a Windows installation cd/dvd which is not usually supplied with laptops anymore. If you can boot windows from the above method I gave you, I believe there are ways of restoring the windows bootloader from within Windows 7, but I'm not familiar with them. If you can get windows to boot, post back and I'll help you search for that method.
If you are fortunate enough to have a Windows 7 installation DVD, here are instructions on how to restore your windows bootloader using the installation dvd: