Canon supports the CanoScan LiDE25 under Windows 7. Go here: http://www.usa.canon.com/cusa/support/consumer/scanners/canoscan_series/canoscan_lide25#DriversAndSoftware
and use the drop down menus to select your version of Windows (32-bit or 64-bit). Note: Windows 7 Starter is only available in the 32-bit version. For all other versions, click Start > Control Panel. Click on System and Security. look for the System header and click on it. Look for the line labeled System Type. Some versions of Windows 7 had the type in the title. (If the Windows version ended in x64, it was the 64-bit version.)
Download and install the Twain driver and the Canon Toolbox if you want the buttons on the scanner to trigger actions at the computer. Note: the third-party software that was on the CD is not available for download on the Canon software.
Windows 8 is not supported for the LiDE25 but the Windows 7 software and driver may work. (However, I haven't tried this myself. You may need to use the compatibility mode. Find the downloads and right click on the exe for each program and choose Properties. In the Compatibility tab, check the box for run the program in the compatibility mode and select the older version of Windows. Then right click again and choose Run as Administrator.)
I hope this helps.