windows 7 not booting after ubuntu partition deletion

You need to repair/reinstall the Windows 7 boot loader.

Use the Windows 7 install disk and choose Repair your computer then command prompt.

Try typing the following two commands:

bootrec /fixmbr
bootrec /fixboot

If it still doesn't work, then try using diskpart and setting the small 100Mb Windows 7 system drive as active, then run the above two commands again. If still having problems or do not understand this step, please say and I will try to go in to more details.

You have to restore something called your "MBR" or Master Boot Record.

The simplest way to do it?

http://www.ehow.com/how_4836283_repair-mbr-windows.html

Note that I found that I had to use the command "bootsect /nt60 c: /mbr" instead of what is given on that site (ie; not 'c:/' or 'c:\', but just 'c:', and a '/mbr' at the end). Assuming that the Windows installation is on C drive that is.