i just recently created a gold card 4 my htc desire hd but my question is do i need to keep it in my phone even after my rom is flashed? or can i remove it and pop in my 16gig class10?
As far as I'm aware the Goldcard is there to stop your phone from checking Client ID things when you flash a stock (unbranded) RUU. Custom ROMs by definition don't care who your carrier is, etc. so you don't need the goldcard in there.
But keep it safe, you'll need it if you ever have to go back to stock.
Exctly .. you require a goldcard only when you are flashing stock rom once its done and you have a bootable rom, you do not required the goldcard.. and as mentioned by gretch.. keep it safe if in future you want to falsh stock rom.