Need to convince Co. to keep WinXP Pro

Have a company with p2p network. Used to have Win2000 pro on (acting server) and Win Me on 3 other computers. Upgraded to WinXp Pro and they believe the problems with their Win Me computers slowing down have to do with the upgrade. Now they want to leave ME (They Think its the best thing since sliced bread) and get rid of XP Pro. Please offer me some real arguements for keeping XP Pro and getting rid of WinME. They mainly share cable internet, access database and printers.