Installation of GNS3 on Windows (7)
VMware Workstation: Download from vmware site.
Loopback interface: Installation of loopback interface on windows 7
GNS3:Download GNS3: GNS3 v08.2 all-in-on, this will intstall all necessary tools and packages.
Cisco router IOS images: Download IOS-images from this location
Cisco ASA firewall IOS and ASDM: Download ASA_IOS and ASDM-645-204
TFTP server: Download and run the setup to install.