I'm doing exactly that right now
I have a Realtek USB WiFi 'dongle' (it says Dynamode 11N USB Adapter on it, but it uses Realtek stuff). The internet gets to my computer via my old phone, tethered via USB. It then goes through the computer and out the USB wireless adapter to my newer phone and iPod as WiFi.
I'm afraid I don't know the exact model of mine, but it looks just like this
. (In Devices and Printers it shows up as RTL8188S WLAN Adapter). I just installed the drivers and bit of software, then in the software clicked on the 'Mode' tab, wher I could switch it from 'Station' to 'Access Point'. I could then choose which internet connection into the PC that it shared, set up a WEP key etc. and then share the connection throughout the house.
hope I helped
(I'm pretty sure the one in the link is the one I have, as it looks identical and they don't list any other similar items)