Follow the steps to install ESXi 5 on VMware workstation 8 on Windows7.
Also I have covered how to upgrade VMware ESXi 4.1 U1 to VMware ESXi 5.0 in below post,
VMware vSphere 5.0 Virtual Machine inside Virtual Machine nested Guests You can Download VMware Workstation 8 & Features from here.
Follow below steps to install VMware vSphere 5 on VMware Workstation,
First Make sure your laptop/desktop processor support Virtulization Technology (VT) & you can enabled it from BIOS.
Select New Virtual machine option in File menu and start with Typical Installation.
Specify location of your Vmware ESXi 5.0 ISO image,
Give Virtual Machine name & location,
For ESXi 5 40GB of Disk size is recommended,
Remove unwanted hardware such as Floppy drive, USB Controller & Sound Card from your VMware ESXi 5.0 Virtual Machine & click Finish.
Now Virtual machine will start, press enter to continue the setup,
Press Enter to Continue,
Accept VMware License agreement,
Now press enter to install VMware ESXi 5.0 on below storage device as shown in screen shot,
Select your keyboard layout,
Enter Vmware ESXi 5.0 root password,
Press F11 to install
Now installation has been completed, so press enter to reboot your VMware ESXi 5.0 Virtual Machine,
Now you can see the installed VMware ESXi 5.0 Build 469512
That’s it, now your VMware ESXi 5.0 ready. VMware ESXi 5.0 in evalution mode will work for 60 days, for further use reapply your ESXi 5.0 license to the ESXi 5.0 server. Now its time to download VMware vSphere Client 5.0, Enter your Vmware ESXi 5.0 Server IP address in Internet Explorer & download VMware vSphere Client 5.0.
VMware vSphere Client 5.0 installation is easy & straight forward. After installation open VMware vSphere Client 5.o & enter your username & password.