1. Ensure that you modem has been completely installed on your
PC. If this has not been done, you will not be able to unlock the device. USB devices have built-in CDROM emulation and installing is as simple as plugging the device in and waiting for the task to end!
2. The correct way to unlock is by inserting a non-accepted SIM card into the device. You should get a box appear asking for the code and once entered the modem is unlocked! Remember that you only get 10 attempts so don't keep trying codes if you get errors!! Some providers have their dashboard software "doctored" so that it doesn't ask for the unlock code! The simple way around this is to download a PC install version of the generic (i.e. unbranded) Mobile Partner dashboard software, you can get that HERE
3. You may want to de-brand your device by flashing new dashboard software to the device itself, for most Huawei devices you can get the upgrade tool HERE
4. Remember that once you have unlocked your device, you will need to set up a new connection profile for the new network. This is done using the dashboard profile management setting under Tools.
Things to remember:
Any Vodafone USB modem with a -Z suffix to it's model number is made by ZTE and thus can not be unlocked with Huawei unlock codes!
The "Flash Code" that is usually also given is only used should you need to upgrade your devices firmware to a version not authorized by your original network. In most cases you will never need to use the Flash Code but if you do, take care that you really understand what you are doing!!
Only ever attempt to upgrade firmware and/or dashboards (unless PC installed versions) with the same model number. For example the E160 and E160G will not use the same firmware because the devices are quite different internally!!