Launching Minecraft lags computer

Whenever I launch Minecraft.exe on my computer, while the Minecraft launcher is loading, my computer starts to lag out. The render rate on my entire computer slows down . This is participially noticeable with moving the mouse pointer or while watching videos while it is starting.

After the launcher has loaded, everything goes back to normal. I log in and I can play the game fine.

I have tried uninstalling all Java installs and reinstalling only the latest Java 64bit with no luck

My computer, operating system install and Java install are all 64bit.

My system specs are as follows:

Operating System
        MS Windows 7 Home Premium 64-bit SP1
CPU
        AMD Phenom II X4 840    38 °C
        Propus 45nm Technology
RAM
        8.00 GB Dual-Channel DDR3 @ 666MHz (9-9-9-24)
Graphics
        SyncMaster (1440x900@60Hz)
        1023MB GeForce GTX 550 Ti (ASUStek Computer Inc)        39 °C

My Java installs are as follows:

Thanks to @SevenSidedDie, I discovered that the error only occurrs when running it with JRE7. This was tested by uninstalling JRE7 and instead using JRE6.

However, as a Java developer, it was really inconvenient to have the the latest Java runtime uninstalled as I need it to debug with. I reinstalled JRE7 and after some tinkering, I did the following to force it to run with JRE6:

Forcing Minecraft to run with JRE6

1. Make sure you have both JRE6 and JRE7 installed.
2. Move Minecraft.exe somewhere out of the way, otherwise it will run with the JRE7 (hence causing the problem). I use the "%AppData%.minecraft" folder.
3. Make a shortcut to Minecraft.exe in your Start menu - You can do this by dragging with your right-mouse button into the All Programs section of the Start menu. Get rid of the "-Shortcut" bit if you wish by right clicking on it and clicking Rename.
4. Right click on your shortcut and click Properties.
5. Under "Target:" enter (with the quotes)"C:\Program Files\Java\jre6\bin\javaw.exe" -jar "%AppData%\.minecraft\Minecraft.exe"
6. Make sure that "Start in:" is set to %AppData%\.minecraft
7. Click Apply and/or OK.

Now, whenever you want to run Minecraft, start it from the Start menu. This also works if you pin the Start menu icon to the taskbar.