Need help loading original rom with sd card

[sabonis]

My activesync has stopped working. The power still charges through the usb, but it doesn't connect. I've tried different usb ports on my pc, I've changed the settings on my phone under usb to pc, and nothing. So, I'd like to reinstall the original rom with a mini sd card. Where can I find the original rom? What do I need to rename the file to(i know I have to, but can't remember). Anything else that anyone can suggest to get activesync back up would be great too. I spazed out and installed this old rom that was on an sdcard and now I lost all my contacts , and have no way of reistablishing a connection to the ol pc. Thanks for any help.