confused!
What did you do? Your Windows died, what do you mean it died? are you getting Operating System not found or is windows complaining of lost files? Can you not just repair the windows installation., which windows? XP/Vista/7....3.11 ....?
Have you installed Ubuntu? or are you booting on LiveCD?
If you installed : did you partition? did you let the installer partition? did you do that funny install Ubuntu inside windows?
Are you getting Ubuntu to install it and to get rid of Windows once and for all? or you getting your feet wet with Linux?
Did you just insert the CD and click next next next next and tadah Ubuntu booted after 30min and a restart?
You need to clarify some of these points, depending on what you have done or what you intend to do, solutions to your problem vary, in some case it may be very difficult to recover data [only partially if partially overwritten] or impossible if complete overwrite....
Solutions can vary from installing ntfs3g (if not installed in Ubuntu, not sure if it is, it certainly isn't in gentoo) and copying your files out to ubuntu from the windows partition, if a bootloader issue loading mssys (available in apt or compile from sourceforge) and writing the bootloader (can be done using LiveCD), repairing windows or installing linux/windows on another drive and running recovery software to recover from the the drive with the windows damaged????, thats only if you've really messed things up and overwritten stuff. Alternatively you can boot to console and chroot if you've messed your Ubuntu up aswell, which is a bit messy so I would recommend LiveCD.
If you know what your doing then the above should give you a rough idea of where to start, if not answer back and I will try to talk you through it, just need a full picture of what happened and what you've done since to the drive.
HTH