A+: Install methods for Win 7*

You can install Win7 from DVD-ROM, from a network, from a USB flash memory drive, from a recovery disc or partition or by restoring a clone image.

Local DVD-ROM: Load the Win7 DVD into your computer's optical drive, boot from it and answer the questions as presented. 

Network install: Install once connected to a network using Windows Deployment Services or Remote Installation Services. Unattend.xml allows unattended installs if you preprogram that XML file for your installation.

Disk image: Apply an entire disc image from external media using apps like Acronis True Image, Norton Ghost or other apps. C:\Windows\System32\Sysprep should be run after applying a clone to alter the Security Identifier (SID) so every PC on a network is unique; if DHCP is not used for automated IP assignment, also change the IP address manually before attaching the PC to your network.

Recovery disc or partition: These contain an image of Windows as if it was installed at the factory. Often the image is on a hidden partition on the PC's hard drive. If the data for your PC is on another partition or drive, e.g., 'D:', then you can recover without erasing your data, and that's a very good idea!

USB flash memory drive: For machines without a DVD-ROM, make a install USB drive by partitioning and formatting it, xcopy the install DVD's files to the USB drive, and set the PC to boot from USB.