AutoCAD 2004 is not compatible with any 64-bit OS. Ignore the workarounds posted in the Autodesk discussions as they do not work reliably. Downloading the MS ORCA and "tweaking" the .msi file and the setup.exe file may allow you to think the product is installing, but the core code of the program was written for a 32-bit system. AutoCAD installed this way will not be stable and some functions that you need may not work correctly, if at all.
In the IT world software and hardware progresses and eventually users have to catch up. You may not like it, but that is the way it is. You can always try IntelliCAD or some other less expensive CAD software if AutoCAD is too pricey. I have worked as a CAD Manager and support technician for a number of years as well as doing CAD work for my own business. Companies I have worked for as their CAD manager have tried to get as many years out of an old version of AutoCAD as they can. But eventually collaborating with other companies and/or the need to upgrade workstations has forced them to upgrade their Autodesk software. The companies I have worked for as a CAD manager have subscriptions for their Autodesk products. I am a one person CAD business and I have a subscription. I bite the bullet every year and pay the price, but I get the latest software as well as direct Autodesk support that non-subscription users do not get. There are people and companies that refuse to go the subscription route because they feel it is a rip off. That is fine too. Like I pointed out, there are cheaper alternatives to AutoCAD. But most of them do not have some feature or tool that you might need.
Daryl Stockton, MCSE