I have windows 7 running laptop. I'm now connecting to the Internet via built-in 3g modem. My problem is that I'm located near to two towers. One of them is providing 3g and second one, only edge signal. My computer is very often switching between them, what is a little annoying. Is there any way to manually configure my modem to connect to the better tower?
You probably either need to change the 3G roaming setting or update something called the "PRL" in your modem.
Typically this would be done by a utility provided with the software accompanying your modem. If it's an OEM device the relevant settings may be buried in some Toshiba "network manager" software or similar. You may try checking the Toshiba website for any utilites available for your model laptop.
PRL updates are pulled from the cellular network and typically can be downloaded automatically, but since it interrupts service usually accompanying software for a cell phone or 3G modem would tell you there's a "service update" for your modem or simliar and require you to approve it before rebooting your device.
You may try seeing if there is a firmware update for your modem as well.