PHP Includes/Requires/opendir/ and accessing files

Hey all, just hoping maybe someone can gently shove me in the right direction.

I'm running PHP 5 on Apache on a Windows 2000 machine, that is connected to a Network.

I have my machine set up as a testing server for an application I'm developing. My web directory is located on my C:\ drive. I have a job set up on another server that downloads data into CSV files and places them on a Network drive, R:\.

I have the location of these files saved in a table as r:/folder/data.csv. One Record for each file I need to upload.

Now, when I try to run my function to upload this file, I get the "Warning, no such file (filename) found in C:\....."

Then, if I try to "include" a file on the network drive I get:

Warning: main(r:/rtss_data/testfile.txt) [function.main]: failed to open stream: No such file or directory in c:\rtsweb\rtss_v_13\test_items\r_test.php on line 10

Warning: main() [function.include]: Failed opening 'r:/rtss_data/testfile.txt' for inclusion (include_path='.;C:\php5\pear') in c:\rtsweb\rtss_v_13\test_items\r_test.php on line 10

If anyone could let me know what I have to do in order to get PHP to access the network drives, It'd be greatly appreciated.!