I have never had issues getting access to the TC from windows..
Have you loaded the latest airport utility for windows and connected by ethernet? Do not attempt to use wireless until you fix the default settings.. which are wrong for SMB.
The TC name and windows names are illegal for SMB networking.. and this causes issues with even iOS stuff.
Change the names.. make them short, no spaces and no special characters.
eg TC name.. TC3TB (you can add whatever for identification, FredTC is fine, but not Freds' TC or Freds'TC even)
Wireless name.. TC24ghz and TC5ghz (use separate name for 5ghz as it will work better). No spaces no dots.. pure alphanumeric.. same with passwords. Use WPA2 Personal.. not wpa/wpa2 mixed up don't know which is which. Password a bit longer obviously 8-12 characters is enough though.
On the disk page put in the windows workgroup name and turn on guest account.
I strongly recommend going back to 7.5.2 firmware. And even I cannot remember how to do it from a PC.
7.6 changed stuff.. although that might affect Mac more than PC's.