I can not make MP3 files with AC 2.02

I have Windows XP Prof servp 3with the latest updates.
I have installed AC 2.0.2 and LAME 3.99 for Windows.
I now open a musicfile MP3 in AC 2.0.2 and made some changes,
and after that I go to “Export” to make a new MP3-file, but that is impossible!
How to fix it?

To avoid confusion / misunderstanding, what is “AC 2.02” ?

Does this answer your question? http://manual.audacityteam.org/man/FAQ:Installation_and_Plug-Ins#lame

AC2.0.2 is= Audacity 2.0.2 naturally!