couple quick questions.
1. where did you get the ROM that you tried to flash onto your 6700?
2. When you were flashing the ROM originally did your handset power off or did you interrupt it while it was doing the flash?
usually if you want to reset the ROM to a Sprint Approved ROM go to
http://www.sprint.com/downloads and select your operating system as Windows Mobile (CE) and the 2nd file listing should be the one for the 6700. If it is not loading then I would set it up to to bootloader mode (as described in the previous post) and try to force the ROM flash. If you're still FUBARed, then I would check and see if you have the Equipment Service & Repair Program on your phone and take it into the Sprint store. Unless you tried to install an aftermarket ROM (e.g. AKU 3.3, most companies that sell equipment don't like you installing ROM flashes not intended from the Manufacturer) they should be able to help you either fix or replace the handset. Just make sure you have all of your data backed up because first thing they'll usually do is a hard reset and try to re-duplicate your problem.