Welcome to Seven Forums and Happy New Year.
Could you clarify the following?
- Are both Ubuntu and Windows on the same HDD or are they on different HDD's?
- What was the order of installation -was it Windows first then Ubuntu or the other way round?
- Can you log into Ubuntu? Are you able to mount and access Windows from within Ubuntu?
Also have a look at this SF tutorial - Dual Boot Windows 7 and Ubuntu
If you want to revert to Windows altogether, then have a look at this tutorial - MBR - Restore Windows 7 Master Boot Record
Look forward to your advice and regards