No your rom *is* screwed. You can get into bootloader, you can even get to 11% of a dopod etc rom upgrade if you try, but you will not flash a new radio.
You CAN boot the device.
Do a hard reset, but do not press spacebar to reboot after. Instead, do a soft reset. The unit should boot but as you've screwed the radio you will not get a gsm signal and the phone will say unknown sim status.
I know this as I bought one cheap after the owner had done exactly the same as you.
IMEI-check's unlock solution is the only one that works IIRC, and in some cases this re-writes the security area of the phone and repairs similar issues, but in this case I could not get the prog to read.
You need to return the device to HTC - you'll need to pay approx £35 for reflashing back to the orange rom. This is what I had to do.
Currently you cannot book the m3100 in through the web as it's too new, instead email / call them.
edit - or if you're an orange customer ring 150 and act dumb saying it ' won't work'.... :wink: