http://techhead.co/running-vmware-vsphere-client-on-windows-7/
The above instructions worked for me [I will copy them here in case the article gets deleted].
Step 1. Get this DLL called system.dll
*Note: This DLL is usually found in the %SystemRoot%Microsoft.NETFrameworkv2.0.50727 directory of a non
Windows 7 PC with .NET v3.5 SP1 installed.
Step 2. Once downloaded install it in the C:Program Files
(x86)VMwareInfrastructureVirtual Infrastructure ClientLauncherLib
directory. If the lib directory doesn’t exist then create it and
drop the dll file into it.
Step 3. Next edit the VpxClient.exe.config file which can be found
in the C:Program Files (x86)\VMware\Infrastructure\Virtual
Infrastructure Client\Launcher directory and add the following three
lines to it in the location specified in the screenshot below. Then
save the changes.
<runtime>
<developmentMode developerInstallation="true"/>
</runtime>
Step 4. From the Windows 7 System Properties click the Advanced
tab and then the Environment Variables button as we want to add a
new System variable.
Create a new System variable called DEVPATH and assign the
following variable value:
C:Program Files (x86)\VMware\Infrastructure\Virtual Infrastructure Client\Launcher\Lib
You are now ready to start using the VMware vSphere Client on your
Windows 7 machine! Some people have reported having to run the client
as an Administrator so if you are having difficulties it may pay to
try this – I luckily didn’t experience this problem. Also you will
likely have to reboot your machine (or restart the explorer.exe
process) for your new path information to come into effect.