When I try to paste something I have copied in Chem3D under Windows XP, I get:
Sorry, the paste command cannot be completed because the specified datatype is invalid.
Versions of Chem3D prior to 7.0 are not compatible with Windows XP. The following may at least help with copy and paste problems, but it is recommended that you upgrade Chem3D.
The solution is to open the Alchemy.TBL file located in the ChemOffice2001\Chem3D\C3dfiltr\ folder using the TblEdit.exe application found in the Chem3D folder, delete a text value (like delete the first name "AG"), add it back, then save the file.
Please note that if you have Chem3D Std or Ltd, you will not have a TblEdit.exe application for editing this file. Your only option is to upgrade to 7.0 or higher.