I continued using Office 2000 for a while after I got a W7 x64 laptop.
I also used it on my XP Upgraded to W7 x64 Desktop.
I seem to remember one machine was fine and the other not. Lots of solutions and counter solutions on the web.
One of the main ones was running winword.exe in XP compatibility mode. Or as Admin. Or both or neither
Start search winword.exe. Right click it > Properties > Compatibility tab
I never got Outlook 2000 working in W7. Switched to Thunderbird instead.
Please post the exact wording of the error message.
Do you get it when you double-click an existing Word Document? Or when creating a New Document? Or both?
Alternatives are Libre Office Free
MS Office Starter 2010 (Word/Excel only with Ribbon interface)