losing mapped drives

Every time I restart a workstation or the server, the workstations lose the mapped drives. Workstations OS is XP Pro upgrade from Win Me. I did not install the upgrade…Me installs are OEM. All workstations running excrutiatingly slow since the upgrade. Server is brand new and running Win server 2003 standard edition and will be used only to house an accounting program. 4 nodes on the network. Peer to peer w/new router handling DHCP addressing.
I think logon scripts will cure the mapped drive issue I’m having.
Will someone please advise, verbatim, as to how to write this type of script. Information I’ve looked at has not been detailed enough to answer my question.
Thanks.