I highly recommend to install Windows 7 on a virtual machine.
The easiest way is to get this tool from Microsoft, called Virtual PC. Short guide inside!
Once you installed VirtualPC,
1. Click on “New” to setup a new virtual machine.
2. Follow the wizard and create a new virtual PC.
3. Enter a random name e.g. “Windows 7 Beta” instead of “New Virtual PC”.
4. Select Windows Vista from the dropdown field because it is the most similar to Windows 7.
5. It will recommend to use 512MB. Follow the wizard and use the recommended amount of memory.
6. Create a new virtual disk.
7. Browse to the folder where you want to install Windows 7. Make sure that you have enough free space there. Enter a certain amount of space for that new virtual disk. I entered 10.000 MB which should be fine to test Windows 7, but you can probably use less here. Windows 7 requires at least 4GB space thou if you do not plan to save anything else on that virtual HDD.
8. Complete the setup.
After you have followed all the steps double-click on the new virtual PC “Windows 7 Beta” or whatever you named it. This will automatically launch the new virtual PC. The top menu of the new window includes a submenu “CD”.
Inside the the submenu “CD” select “Detect ISO-Image” (could have a slightly different name) and locate the ISO file you downloaded from Microsoft before.
Note: You have to restart the virtual PC after the tool detected your ISO file.
Voilà now you can try Windows 7 without risking to loose any data at all!