Windows 7: Performance with Windows 7 and Laptop(i5 processor)

We have a standalone application which was originally developed in Winforms but now we are gradually migrating it to WPF.
As of now its partly Winform(60%) and partly WPF(40%). We have already done few releases of the application and things
were fine. Recently several of our colleagues upgraded to new laptops and they are experiencing strange performance issues
with our application. A simple drag and drop operation (within the application) is taking 10-15 seconds. The same scenarios are
working fine on Desktop systems.
This is particularly surprising because the laptops have better configuration than the Desktops on which performance is fine.
I am giving below the configuration of Laptops and Desktops used:
Laptop:
Processor: Intel(R) Core(TM) i5 CPU M540 @ 2.53GHz 2.53 GHz
RAM: 4GB
System type: 64-bit Operating System
Desktop
Processor:Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz 3.00GHz
RAM: 4GB
System type: 64-bit Operating System
Can anyone please help us in identifying the cause of this issue.

Your processors aren't even close to the same.

They are from two different families. The Core 2 series was made using a larger process and slower/older memory controllers. The Core i series using onboard memory controllers, self-overclocking, is a physically smaller chip so it runs with less power (typically).

Never compare clock speeds when comparing two families of processors. You will not have equal measurements.

However, in your case, it sounds like the processor is finding it doesn't have enough to do most of the time and is slowing down (by design) and all of a sudden when your app requires it's full glory (regardless of what you are doing) it's freaking out because it's pants are off. You have to think about, as well, what this "drag and drop" operation really is. It may just look like you're moving something but there's tons (technical word) of variables involved if the app is complex.

Please clarify the following:

RAM: DDR2 or DDR3?
OS: What version?
HDD: Details?

Hi Johnathan,

Thanks for your reply. Following are the details(of the laptop having i5) you asked for:
RAM: 4GB DDR3
OS Name: Microsoft Windows 7 Enterprise/
Version: 6.1.7600 Build 7600
HardDisk: 300 GB || Manufacturer: (Standard Disk Drives) || Model: HITACHI HTS725032A9A364

And the "drag and drop" that I mentioned is just one of the examples of how slow the application behaves. Overall most of the operations are slow. For e.g on mouse left click on one of the controls within our application launches a popup window. Even this takes lot of time.

Regards,
Pankaj