If you did not install windows 7 to the same partition you had Suse Linux on you should be able to boot it. Windows installations will overwrite the master boot record without asking if you want to do that or informing you it is being done.
Two options: From windows 7, go online to the neosmart technologies and download the EasyBCD program. You can use that to boot your Linux. I would suggest reading the documentation or their how-to before doing anything.
You can reinstall Grub and put an entry it its configuration file for windows 7. To give you advice on this, we would need your partition information which you can get by using any Linux Live CD, booting with it, open a terminal and typing : fdisk -l (lower case Letter L in the command, not a number one). You could also download a Parted Magic CD
and do the same (smaller download if you do not have a Linux Live CD).