Real solution to disable activesync in Windows Mobile and PC

In Windows mobile, use the fake server method:
1. Tap the menu tab/soft key and tap "Add Server Source"
2. Configure a server source with a dummy IP address, user id, password and domain name; these do not have to be real
3. Once configured you should have another sync source show up on your main AS screen...continue on.
4. Tap the menu soft key again and you should see that the sync schedule option is no longer greyed out.
5. Change your schedule from a timed automatic start of AS to manual under both fields
6. If you try to sync now, AS will try to contact your imaginary exchange server and that will take forever until it times out, so you can now delete the exchange server from your list of sync sources. Your changes to the sync schedule will remain and will survive soft resets too.

In PC
In the above-shown Task Manager, kill the process named as wcescomm.exe.

Then, when you want to restart ActiveSync, just click Microsoft ActiveSync to restart it.