First of all, I cannot test it fully since I only have a phone with wm6.5 flashed on it, but the time I tried it, it worked. So if you try this, it's on your one risk.
So this works on WM6.5 phone where no widget engine has been cooked in, but it could work on other WM versions, so if you have tried it on another versions, post it here.
Afterwards do a softreset and try a widget. For example one I created which can be found here:
Note, if you do have the widget engine but you can't open .wgt or .widget files, just use this cab: enable_widgets_wm6.5.cab. If the file \Windows\wmwidgetinstaller.exe does not exist then you can try the cab with the whole widget engine.