Network browsing in XP 10 Times Slower than Win98

I had some old computers, but now I bought new ones and want to install XP in all of them.

The problem is I need a fast browsing in one network machine (let's call it Server) running Windows XP, because it stores lots of MP3 and other files.

When browsing a folder with many files (1700 files more or less), a Win98 machine takes 1 second to list everything while XP takes more than 10 seconds!!! The response time in XP depends on how many files the folder has, while in Win98 it is constant.

I searched Google and tried some tips... but nothing speed the browsing up.

I think it's some XP configuration, because if it was the network it couldn't be fast in the Win98 machine, right?

All windows machine (including the MP3 server) are connected to a switch. My network is:

ADSL Modem --- Linux (just for Firewall) --- SMC 1024DT 24 port Switch --- Windows 98 and XP Machines

Any one can help me? Dividing the files in many folders is not an option... I must have all of them in one folder only.

Thanks