Maximum Respect to Matterhorn for the tutorial below 
It is a bit complicated.
1. Uninstall Voice command from the Jam AND your PC.
2. Clear out your Jam internal storage memory, cut it to your PC for example.
3. First disconnect your Jam from the PC. If you have Voice Command 1.50 full ver. install that to your PC, if you have Ver. 1 install that and then install the 1.50 upgrade.
4. Look for a file called C:\Program Files\Microsoft Voice Command\Windows Mobile Pocket PC\US 1.50\Microsoft Voice Command US PPC 1.50.PPC420_StrongARM.CAB on your PC.
5. Make sure that you have the CABInstall program on your Jam and have it intercepting your CAB installs.
6. Copy the Voice Command CAB file from your PC to an SD card and Install Voice Command CAB by clicking it with your Jam file browser. CabInstl should launch and ask you where you want to install the CAB file. Make a new directory in Internal Storage for Voice Command, either before hand with your file browser or with Cabinstl. Now install the CAB to that location, that’s it.
If you want to install other big programs like Pocket Informant and Resco to internal storage, it is best to do them directly after this, before adding a lot of other little programs, this allows for enough install space for those “biggies”.
Good Luck