Managing Legacy Systems

Hi!

I currently manage the IT dept. of a chain of supermarkets with at least 300 computers with mixed os. new computers running on winxp pro or win2k pro. legacy computers run on win98se.

Although there has been no problem in managing systems with winxp pro and win2k pro, i have heavy headaches on win98se computers.

My main concern is desktop security. anybody got an idea or anybody can give me some workarounds for win98se desktop security.