Apache console <> service on WinXP

Hi,

Here's the situation: I'm building an intranet for my company, on this
intranet there's a certain page where users can see a directory
listing of a network drive (g:), mapped on the server. This PHP-page
uses the opendir function to retrieve directory information.
The problem: when I start Apache as a console application everything
works fine, but when I start it as a service, the opendir-function
doesn't seem to be working. And the Apache-service is logged on as my
account, not localsystem. Even stranger: accessing the folder via an
alias /group, which points to the same network drive, always works.
Is there anybody who has any idea what I'm missing here?

Thanx,
Bob.