Whatever storage device you have the TM backup on is likely formatted HFS+, so you’ll need to find a way to access that kind of filesystem on a Windows computer.
You can use HFSExplorer to perform such a feat. Just be sure you have Sun’s Java runtime for Windows installed ahead of time.
Lastly, once you have read access to the disk you’ll want to browse to Backups.backupd/<computer name>/Latest should get you your latest backup. Your documents will be in the sub folder <hard disk name>/Users/<user name>.