We set up some OPACs for catalogue searches on old PCs with a light weight linux, works great. Not only is it fast all round but so locked down anything a student tries with just restarts the browser. So I will join the above linux camp as the best option, there's also an open source client "VMware View Open Client".

I agree linux can seem daunting if you have not touched it before (or any UNIX/BSD), but consider a trusted student who has an interest in it to help you.