To eliminate the possibility that the bat file is not working did you go the command prompt? Just type:
cmd
Try
subst /?
It will just list all the commands, but at least you will know its found by the system.
Then try:
subst P: C:\ArmAWork\
Quotations are needed if there is no space in the file name.
DISCO! This worked!

Buldozer could be fired up now from O2 without a problem. P drive was now found and installed through cmd. Big thanks for putting uyp with my ignorance! And very big thanks for your help guys. tcp you the man

Now i need to know what i should look out for, as i have now moved the entire folder to a different location. Will this somehow be a problem with anything...? What should i pay attention to now. Some folder paths that need changing somewhere or...