When Orange released their AKU 2.0 ROM for the C600 it introduced a much tighter security policy. A previous loophole for changing security policies involving a signed registry editing application was closed by black-listing the app. Also the online unlocking page from the Orange Developer program doesn't recognise a C600 IMEI. Luckily there is a process in place to get your device unlocked for development and testing. Here are the steps to take, you'll get up and running in a day or two:-

Send an email to developers [at] orange [dot] com

Make sure you include all the following information:-

• IMEI of the phone exactly as displayed when you dial *#06# (17 digits long)
• Your full name
• Your orange network country
• Phone number for the handset (must be an orange number)
• Full model number of the device

Using this information they prepare a special unlocking app specific to your device, you should get this back within a couple of days. They will send you this as a zip file with an executable which will run on your desktop and install the component to your device over ActiveSync. On your Smartphone you can then run the tool from Start > Accessories > Security Levels. You can then change the security model to Disabled, Low or High at any time. Turn the phone off and on again for the change to take full effect.