Server Issues - HELP!!!

I've set up a server on my XP pro computer. It works pretty good, unless I try to send data via ASP to an .mdb file.
I keep getting the same error over and over. Sometimes, the error dissapears and I CAN send data, but usually I get the following message:
"Microsoft OLE DB Provider for ODBC Drivers (0x80004005)
[Microsoft][ODBC Microsoft Access Driver] The Microsoft Jet database cannot open the file '(unknown)'. It is already opened exclusively by another user, or you need permission to view its data."
I have downloaded the latest Jet, whatever it is, and installed it. As far as I know, I haven't tampered with any of Access' setting. I have Office 2003 installed, it it makes any difference.
Thanks in advance