If you want better performance, you should go for a "real" NAS solution, like the Buffalo Linkstation Pro or something like that. From that I get around 10-11 MB/sec read/write with SAMBA over Ethernet.
I dont have Gigabit, but the devices does support that. As 11 MB/sec is very close to 100Mbit, I dont know if the limit I see is the network or the device.
Accessing the WinXP client that you have directly on the Trendnet router FROM one of the PC's connected to the ASUS Should work out of the box I think !
Kalin: No worries. All questions are welcome, if someone has a hot temper and can't undestand that not everyone is at the same skill level, they should either exhale or consider not reading the forum