How do I install Windows 95 on a computer with MS-DOS and Windows 3.x on it?By: Arie Slob
Microsoft recommends you to run the Windows 95 setup from within Windows 3.x, which does work, but if you plan on installing Windows 95 in a separate directory than your existing Windows, you should run setup from DOS instead.
Make sure that all your peripherals work properly with Windows 3.x before you upgrade. If you don't plan on dual booting between Windows 95 and Windows 3.x and you just can't wait to install all your applications from scratch again (?), it is still the best to install Windows 95 from scratch! It will take some time, but you will have the best chance of a good working Windows 95.
If you installed Windows 95 "on top" of Windows 3.x and you experience a lot of errors which you can't explain, try installing Windows 95 from scratch! (meaning: start with Format C:). Just back-up all your data files, and check that you have all the installation disks. See How do I install Windows 95 on a computer with nothing else on it? for more details.
If you encounter difficulties installing Win95, try Microsoft's Windows 95 Support Center.