Start by installing Airport Utility. This can be downloaded through Apple support, or simply search google e.g. “Airport Utility Windows Vista or 7.
After installing the utility all you have to do is this:
Go to -> C:\Program Files\Airport
Click on -> APDiskPrefs.exe
Click -> Automatically Discover Airport Disks
Click -> Show Airport Disks in the system tray
Look in the system tray (at the lower right corner of your screen), click on -> Airport Base Station Agent
In the menu click -> [the name of your Time Capsule]
Choose -> Connect with Password
Type in the password and click OK. Now your Time Capsule will be visible in My Computer, under Network drives (no mapping required!)