I have an ASUS RT-N16 with "tomato(shibby)-K26USB-1.28.RT-MIPSR2-105-Mega-VPN", and Windows 7. The router is not showing anywhere in the networking dialogs, but I am connected OK via wired and wireless. Tomato does mount my USB hard drive and I can see its files via telnet. But until I can see the router as a network device in Windows I can mount it there.
Is this a tomato problem or a Windows problem? (NOTE: when the router had the stock ASUS firmware it was detected by Windows just fine).
I have checked all the tomato settings but can't find anything specific to this issue.
[EDIT] problem partially fixed, I needed to update Hostname in Router Identification to "workgroup" to match default Windows config, then rebooted router. This enabled me to map the HDD to a letter, which persists across restart and hibernate. However, workgroup appears/disappears at random from the file system, making it not useful. There is something different about the way tomato is interacting with Windows 7 compared to the original ASUS firmware.
For more info about his topic see thread with title "Map a network drive? Please, please help" posted 5 Nov 2011