XAMPP cannot access htdocs via Internet

[Frozen27]

Hello ,
I have installed XAMPP v 1.7.7 on my PC and i have no problems operating it, i can access my htdocs files with localhost, 127.0.0.1or with my static network ip. I cannot access the files from another PC via internet (i have a static internet ip). I do not use a router, however I currently have internet from an USB Modem. Any suggestions ?

[JonB]

It might be useful to know what version of Windows you are using