Installing a 32 bit on an original 64 bit system

One additional tip regardless of whether you install 32-bit or 64-bit Windows 7.  Clean installs of Windows 7 are extremely painful these days because there have been so many years of updates since SP1 (which came out in February 2011), and the catalog is now so large that until you install a relatively recent patch, Windows Update can hang for literally hours trying to even figure out what updates need to be downloaded, before you even start downloading hundreds of updates and rebooting multiple times to get everything installed.  However, you can make this drastically simpler.  Microsoft released a "Convenience Update" that includes every update from SP1 through April 2016 (that's 5 years of updates in a single package) and then the rollup that includes the fix for long Windows Update scans.

The instructions and download links for the Convenience Package are here - make sure you also grab the small Servicing Stack update, since you have to install that and restart before you install the Convenience Update.  After that, download July 2016 Rollup KB3172605, which includes the Windows Update fix.  At that point it should become a lot less painful to get current.

@Sirfredrico"Sell support only shows drivers for a 64 bit OS. "

Hello. You can see all of the drivers that Dell has released for the Studio XPS 1647 here. I didn't check each & every one, but it looks like most items do have a Win7 32 bit driver available.

It might, but a 32-bit OS would only be able to use 4GB of RAM total, and no application would be allowed to use more than 2GB.  You can download a 64-bit Windows 7 installer directly from Microsoft here: https://www.microsoft.com/en-us/software-download/windows7

Go to Device Manager, and if you have an unknown network controller device somewhere, open its Properties, go to the Details tab, select Hardware IDs in the dropdown menu, and post its 4-character VEN and DEV strings.

The WiFi card is the Intel Ultimate-N 6300.  You can find the latest Windows 7 drivers for that card here: https://downloadcenter.intel.com/download/27238/Intel-PROSet-Wireless-Software-and-Drivers-for-Intel-Centrino-Ultimate-N-6300?product=59474

The ACPI device is probably a chipset driver.  Go to support.dell.com, try choosing your system by clicking "Select from all products" instead of entering your Service Tag, then go to Drivers and Downloads and select Win7 64-bit in the OS dropdown.

As I said, try going to support.dell.com, selecting your model (rather than entering your Service Tag), selecting Drivers & Downloads, choosing Windows 7 64-bit, and then getting the drivers that are available there.  Dell provides full sets of drivers for all of its systems.  Of course in some cases there are multiple drivers that aren't all necessary because the system was offered in multiple configurations -- like multiple WiFi cards being available.  Next time you might want to look through Device Manager BEFORE you wipe your system to see what you have and download the appropriate drivers in advance.  But once you figure it out this time, you may want to keep a set of driver files stashed somewhere for future use.

Alternatively, you could try downloading Dell Command Update.  I don't know if it works on older systems, but if it does, it will automatically scan your system to figure out what drivers are required and then guide you through downloading and installing them.