i think you can find an answer at:
www.autodesk.com which is the website of autodesk company the creator of autocad , I hope you can find a contact email address at this website.
dear friend:
at sap2000 we convert the old sap90 files to the new sap2000 files by going to file menu-then clicking on "import" word and then clicking on sap90 word.
I think there is a same option at etabs because etabs and sap are both from one company. and if you have any more...