alrite thanks, now it just instantly closes, I tried adding --system("pause") at the end and that didnt help either. Thanks for help, I'm not much of a programmer, and GUI miner seems to think 4850s dont have OpenCL.
Add a new line after the last just containing "pause" without citation and it should leave you with a "Press any key to continue..." and hopefully the error output of your miner.
And try with the entire mining path + parameters in citation.
start /D "C:\poclbm\" "poclbm.exe --host=deepbit.net --port=8332 --user=xxxxx --pass=xxxxxx --device=0"