u should have a com 1, just about every computer has a com 1, i cant think why it isnt displayed unless its been disabled or try pressing delete button or f2 on computer start up right at the start to bring the bios screen up, its hard to say coz there are loads of difference bios screens from computer to computer, but its the same, have a look for com 1 within the bios screen somewhere to see if its says anything.............

xp should pick up the com port from startup if its been deleted, hence why i say it may be disabled or conflicting with another port