Setting up your PC to boot in Windows 95 and Windows NT is a method to use when you only have one machine available and you need to have both operating systems at your disposal.
Your hard drive(s) must be formatted as a FAT(also called FAT16) partition in order to be able to boot in either operating system. Windows NT cannot be installed on any hard drive that is formatted as a FAT32 partition, nor can it view data on drives with that format. Windows 95 cannot view data on a hard drive formatted as an NTFS partition.
With your hard drive(s) formatted as a FAT partition, here are the steps to follow for the dual boot:
1. Install Windows 95. If you already have Windows 95 installed, you don't need to reinstall it unless you need to reformat your drives because you don't have the proper kind of partition.
2. Put in the Windows NT CD-ROM. It should auto-run and bring up a window with a button to "Install Windows NT". If not, go into the /i386 folder and run winnt.exe.
3. NT will start to install and either prompt you for information or run on its own without prompting you. After it is finished the first phase of installation, it will restart your computer.
4. In the second phase of the installation, NT will display your drives and partitions. It will also ask which partition you want NT installed upon. Select any of the partitions that are FAT (you can even select the one that Windows 95 is on). When prompted for the partition reformatted, be sure to select that you want to keep the existing file system intact. NT will install to /winnt, not to /windows, so it won't overlay Windows 95.
5. The installation process will continue, with numerous reboots. NT will automatically set up a dual-boot menu.
Once completed, upon booting the system you'll see a menu that has three entries similar to this:
Microsoft Windows
Windows NT Workstation Version 4.00
Windows NT Workstation Version 4.00 (VGA Mode)
A countdown timer will start, and automatically boot into the first option in 30 seconds unless a key is pressed. Select the option you want and press enter. "Microsoft Windows" will boot your previously-installed Windows 95. "VGA Mode" for Windows NT is much like Windows 95's "Safe Mode".
To change which option is booted by default, boot into Windows NT, right-click on My Computer and select Properties. One of the tabs is "Startup/Shutdown". From that tab you can select which item is booted by default, and how long the default countdown time is set for.