classnotfoundexception

i have a cd we created that is a html document with links to word documents..the program works fine on hard drive…it uses mouseovers, etc..but when i burn all the files to cd also the class files, and it will not work…it brings up the sheet in internet explorer but my buttons are just gray and when you hoighlight them it says “classnotfoundexception” error…why is this? i use windows 2000 pro..i tried it on a win 98 machine with virtual machine installed and updated on it with i e ver. 5.0 and it worked…my win 2000 versions are all higher than those what is going wrong here…please give me some guidance on how i can fix this…
thanks