Sorry, you say you have downloaded the file to your Laptop and tryed installing it from there.
If the file is still on your laptop, check to see if its a CAB file if not go back to Adobe and look for Macromedia Flash Player 7 for Pocket PC. Download the CAB file to your laptop.
Pop you X51v into your ActiveSync and copy the file over to your device. Put it into a Temp folder or on the SD/CF.
Go find the file on your device and then just tap it. It should start loading.
You should Soft Reset after it's finished.
To check to see if it is working ok, go here:
http://tvnz.co.nz
Here is the CAB file to save time:
http://download.macromedia.com/pub/f...fp7_ppc_en.cab