ADT 3.3 - AutoCAD 2004

Any one had this problem, I have recently encountered. I am running ADT 3.3 and AutoCAD 2004. For months there were no problems with this, but recently when I
hit the shortcuts to run the programs I get the following message when starting ADT, "A required DLL file, AC1ST15.DLL, was not found" and when starting AutoCAD 2004 "A required DLL file, AC1ST16.DLL, was not found." I have been the obvious route and re-installed the software and they worked fine for a couple of days then started doing the same. By doing a search for the so-called missing files, finds them in the following directories (folders): ac1st15.dll in "C:\Program Files\Common Files\AutoDesk Shared" and ac1st16.dll is also found in this directory (folder). If I right click on the dll file and follow the "open with" command and use acad.exe to open the file ADT 3.3 opens when both files are opened in this manner. AutoCAD 2004 does not open. I read a post further down where someone had a problem because they had real player installed. I have had real player for years and not had a problem, but it did upgrade itself recently. Mmm? I am running win98se on a Sony vaio laptop P2 366Mhz. If any one has any ideas I'd welcome them, meantime I am off to remove and re-install.
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