500 - Internal server error.
There is a problem with the resource you are looking for, and it cannot be displayed.

The OS is Windows 7 and its of 32-bit OS type

After publishing I get the above error. This OS is Windows Server 2008 R2 and is of 64-bit..

I have changed the Platform from Any CPU to x86... the error still remains

I tried to change the target Platform to x64 and also to x86...
Application Pool's default setting for Enable 32-Bit Applications was False and I set it to true as .. Nothing worked!

Can anybody tell me if I have to change the Platform field or Target Platform field? and what should I change it as?

Ketsuekiame commented: Lied about attempted resolution steps as the OP proves by their own "solution" further in the thread. -2

You could try running it in XP Compatibility mode.

Did you check the Event Viewer for any errors in IIS? Also verify that the Application Pool used for the website (which I assumed it is) is correctlly set and started. Verify the .Net Framework for the App Pool. Did you run aspnet_regiis ?

Does the 500 page give you an exception stack? If it does, pasting that will help determine the cause. Unfortunately the error code 500 just means something went wrong. It's a very generic error code :(

@Pitic and @Ketsuekiame I found out a simple solution (for which I slogged for 2 days).

In the Application Pool -> Default Web site -> Enabled the 32-Bit Application Pool and set it to true.. (Default value is false).

This resolved the 32bit and 64bit compatibility issues and 500 Internal server error problem !

You said you already did that in the first post...