Windows 7 re-installing windows 7 x 64bit Professional on Dell XPS1645

[magnavrx]

Hi.
I have a Dell XPS1645 Studio which came with Windows 7 x 64 bit Professional installed some 3 years ago. Last year I built a new desktop PC for work purposes (research Human Mechanics/ Motion). (Samsung SSD 128G 830, IB i5-3750K CPU, GTX66oTi, 16G xDDR3 Ram, Asus Sabertooth 77 M/B, etc). The Dell has served me well and I would like to keep it, it has recently run out of it's 3 year warranty.
I want to exchange the hard drive in both computers.
I came up a little short in my estimates on the SSD for the PC build with only 128G (the OS, programs etc take up more than the 50% mark and I can't trim it down enough.
The Dell has a standard drive which I would like to replace with a top end SSD. The 128G SSD from the PC would be OK for the Dell and I would replace the 128 SSD currently now in the desktop PC with a Samsung 840 250G as main drive, with existing 1TB Samsung HDD to remain as storage.
I have a number of high end, 500G-1TB external drives I can hook to the laptop for storage.
I have the retail pack Win 7 x 64bit Home premium disk for the PC. The Dell was OEM but the serial number is still on the Dell laptop. Both computers are in a Homegroup network and I also have an Apple iPad3 also linked.
It would be nice if I could take the SSD from the PC and slot it into the Dell laptop and do a clean install in the Desktop with the Retail Pack I have on a new 250G SSD, but I guess there is no known way to do that?
Where do I download Win 7 x 64bit Professional for clean re-install to the laptop?
Thanks for any advice.

 

[voyager]

To smooth this out in my mind:

You want to install new [to the PC/Laptop] HDDs &/or SSDs to hold the OS partitions in the PC and laptop.

Unless you have a reason to do a clean install, you could make images of the present OS partitions, then install the images onto the respective replacement drives.
As long as the replacement drives are >/= the drives they are replacing, there should be no problem with fitting the images onto the new drives.
If you need to deal with AHCI enablement see:
http://windows7forums.com/windows-7-support/91708-dreaded-ahci-issue-twist.html

If you must do a clean install onto the laptop, you will need an OEM copy of the Win7 version you want to replace, maybe even a Dell OEM copy.
Being as the desktop is a homebuilt, you will have more latitude.
If the laptop is like any Win7 manufactured desktop, the BIOS, Win7 version and product key all have to match correctly for a successful replacement of the OEM install.

Sorry for no satisfaction on finding the Win7 OS discs.