If your windows partition is still ok, you probably just have to set it in your boot manager. I'll give you a short instruction on how to do this if you run grub, if you have another boot manager (probably lilo then), google yourself some manual.
edit the file grub.conf as root (/etc/grub.conf or /boot/grub/grub.conf or whatever... try 'find / -name "grub.conf"')
paste the following on the bottom of the file:
then check this line:
The X is the time your boot loader will wait before booting the default, make sure it's an appropriate value.