The nicest thing about windows 7 (and I have done this more than once), is that you can copy the contents of the Win 7 DVD onto a usb hard drive and replace the install.wim file in the sources directory with the install.wim file that you create after imaging your computer as Glenn suggested. Obviously you need to make your usb hard drive bootable. If you decide that you want to go back to windows 7, just plug in the usb hard drive and boot off it and start installing windows.
Bear in mind, before you can capture the image, you need to sysprep it, otherwise you cannot capture it. Or at least ways this issue occurs if you are booting from a windows deployment server. I have not booted the computer without a WDS server to capture the image, as I have never needed to do that. But I assume that your computer being at home, does not have a windows WDS server to boot off.
Otherwise just use an imaging program to image your computer onto your usb hard drive, if you find the microsoft way too difficult for whatever reason. Again, good idea to sysprep it first, even though you are not doing multiple cloning.
Hope that helps.