From Forum Nokia Wiki

In case you have multiple SDKs installed on your machine, you can switch between them and select the default device by these steps:

Go To Command Prompt

C:> devices

It will list down the installed SDKs and the default one.

To set default Device:

devices -setdefault @DeviceID

Example:
Following shows S60 3rd MR edition is set as default.

C:\>devices
S60_2nd_FP2:com.nokia.Series60
Series60_v20:com.nokia.series60
S60_3rd_MR:com.nokia.s60 - default
Series80_DP2_0_SDK:com.nokia.Series80

Now if you want to set S60 2nd FP2 SDK as default, do the following:

C:\>devices -setdefault @S60_2nd_FP2:com.nokia.Series60

Finally you shall have S60 2nd FP2 SDK as default SDK.

C:\>devices
S60_2nd_FP2:com.nokia.Series60 - default
Series60_v20:com.nokia.series60
Series80_DP2_0_SDK:com.nokia.Series80
S60_3rd_MR:com.nokia.s60