First, have you installed it on the network?
Ensure you're connected to the Time Capsule's wireless network. Go to System Preferences > Print and Fax > click the "plus" button in the lower-left hand corner > wait for the printer list to refresh > click your printer > click Add.
On the Windows 7 computer, you're going to have to install Bonjour, which comes on the Time Capsule CD. Insert the CD, install the software, then click "Bonjour Printer Utility" in your programs list.
If you've already done this, sorry! Just checking!