Hi everyone in this article I’m explaining about installWindows 7 without the disc.
 

Details:

Assuming you have the product key, you’re sorted, as it’seasy to download the installation files for Windows online. You will, however,need to know exactly which version of Windows your product key is for.
 

Step 1.  Go to the Control Panel, then Systemand Security, and finally System. Along with other information about your PC orlaptop, this will tell you precisely which version of Windows 7 it is. Keysshould work with either 32- or 64-bit versions of Windows 7, but you can’t swapfrom Windows 7 Home Premium to, say, Windows 7 Ultimate.

Step 2. Armed with this knowledge, click one of the linksbelow where you can legally download an ISO image of the required installationdisc:

  Windows 7 Home Premium 32Bit:

http://msft.digitalrivercontent.net/win/X17-58996.iso

Windows 7 Home Premium  64Bit:

http://msft.digitalrivercontent.net/win/X17-58997.iso

Windows 7 Professional 32Bit: 

http://msft.digitalrivercontent.net/win/X17-59183.iso

 Windows 7 Professional 64Bit: 

http://msft.digitalrivercontent.net/win/X17-59186.iso

Windows 7 Ultimate 32Bit: 

http://msft.digitalrivercontent.net/win/X17-59463.iso

Windows 7 Ultimate 64Bit: 

http://msft.digitalrivercontent.net/win/X17-59465.iso

Step 3. Now you have the disc, you need to burn it to a DVD,or extract it to a suitable USB flash drive. You can’t simply copy the ISO fileto a flash drive or DVD. Instead, you need a tool to do this, such asMicrosoft’s own USB/DVD tool Microsoft’s own USB/DVD tool

Alternatively you can use the tool we recommend in ourguide: How to install Windows 7 from a USB flash drive.

Step 4. Shut down your computer and insert your DVD or USBflash drive. Now power on the PC and it should boot from the disc or drive. Ifnot, you’ll need to enter the BIOS and change the boot order to prioritise theDVD drive or USB drive.

Step 5. When you get your computer to boot from the disc orUSB drive, you can install Windows 7. Be careful, though. If you’re planning todo a fresh install and format the hard drive as part of the process, make sureyou’ve backed up all your documents, music, photos, videos and other files youdon’t want to lose.

 Check more posts on windows 7 troubleshooting here