To use E398 as Bluetooth modem simply connect to Internet via Motorola Phone Tools.
You can also connect via Windows itself. On Windows 7. Right click on Bluetooth icon next to clock. Add device. You have to pair your PC and phone with a code. When it is done Windows installs necessery drivers. Then doubleclick on your phone icon and then there are options like browse files on your phone, use computer as BT headset and also connect to Internet. Just click connect.
I use phones as Bluetooth modems because it is more convenient, my tests did not show any difference in connection speed, you can have your phone plugged in (important with E398, because it wont charge over USB).
I haven't tryed E398 with Win7, but it connects this way with V6 maxx.
There are many webpages where you can test your connection speed. I use
http://www.ruuter.ee/kiirus/?download Lühike test is short test that loads a megabait.
Käivita test starts the test. Wait and you'll see your connection speed.