As you may already be aware, 32-bit operating systems (Windows or otherwise) can only use 4GB of RAM.  Windows reserves a portion of those 4 billion addresses for hardware interaction.  Because these addresses are reserved, not all the RAM is "usable".  The actual amount of  "usable" RAM can vary between 3.25 and 3.75, depending on the actual hardware needs of the system (video, add-in cards, and other integrated components are the biggest variables).

Do both SC430's have the same OS and edition (Professional, Enterprise, etc.)?

In the SC430, it all comes down to the processor it is outfitted with.  If the processor supports 64-bit, then you can install a 64-bit OS on it - provided you can find x64 drivers needed for any device not supported natively by Windows 7.

Thank you for the reply.

If I move the 4-GB RAM to the other SC430, I get 3.6-GB usable RAM.  And the two SC430's are equipped equivalently - dual 80-GB SATA drives, same video card (which uses 1.4-GB of shared memory), and same sound card - with same updated drivers and BIOS-level (A04).  One SC430 says 3.25-GB and the other SC430 says 3.6-GB usable RAM.

I ask, can I install Windows-7 64-bit onto these computers?  The BIOS mentions 64-bit in the processor information.  Has anyone tried installing 64-bit Windows onto an SC430.  (64-bit is an option for downloading drivers.)  Or am I venturing into an uncharted area?

Thank you.

To add to theflash1932, even if you do upgrade to a 64-bit OS, the system bios on this system may or may not support remapping the hardware memory to the higher regions (over 4GB). With a 64-bit OS, it may report the whole 4GB, but without the chipset and/or bios being able to remap the memory, you still wouldn't have access to the whole 4GB.

Thank you for the reply.

To answer theflash1932, both SC430's have Windows-7 Professional Edition.  And the devices attached are very similar if not identical.  I have added a PCI video card (Nvidia 8400gs with 512MB by PNY)  and a sound card (Diamond MM Extreme Sound 5.1) - both are standard PCI (not PCI Express) and they seem to function OK.  Upon boot, both load 57 processes and use 1.3-GB of Memory (as reported by the Task Manager).

I noticed DELL has an Intel chipset update (urgent update) for the SC430.  However, when I try applying it, I get the message the operating system is not supported by this update.  The update is: R101519 and is intended for Windows XP, Windows 2003 Server, and Windows-2000.  Is there any chance DELL may update that update to include more current operating systems?

I think I may try the Windows-7 64-bit Professional Edition install this weekend (fresh install, wipe both 80gb HDD clean). 

I want to take a moment to complement DELL for these two SC430's.  They are a good computer - giving me little problems until this.  In June (after 4-years of use in my home-based test-lab), both power supplies ceased within ten days of each other.  I acquired new power supplies and the units are still running strong.  They have the Pentium-D 2.8GHz processor with hyperthreading.  The SC430's have been well worth my investment about 4-1/2 years ago from DELL Outlet.

That's a good point that I forgot to mention.  One of my laptops is x64 with 4GB RAM, showing usable 3.75.

Thank you for your reply.

I too have laptops.  I recently bought a Dell Latitude e6510 with the i7-720QM processor.  That has Windows-7 Ultimate x64 installed.  Windows' System is showing 4-GB RAM installed (and usable).  The RAM in the laptop can be upgraded to 8-GB RAM (which I am looking at doing before end-of-year). 

The video / graphics cards with their "shared memory architecture" appear to be eating up the RAM in both of my SC430 computers.  Both have 512MB video cards from NVIDIA.

An FYI: I own two VisionTEK / ATI x1550 video cards with 256MB RAM.  They use up less than 1GB of system memory compared to the PNY / NVIDIA cards with 512MB RAM that use up 1.4-GB of system memory.  I thought surely installing a video card with more dedicated memory would use less of the shared system memory.  I guess ATI does some data compression to fit more data into lesser available memory.  My PC is running 1680x1050 on a 22-inch monitor.  My laptop is also using 1.4GB (with its NVIDIA 3100 video card).  Am I missing something? 

I rebuilt the SC430 using 64-bit Windows-7 Professional.  To my surprise, the 4-GB RAM, still only 3.25-GB is usable.

I thought I'd report back here the results.

Thank you.

Since the SC430 only supports 4GB, I guess that makes sense ... the system has no where else to allocated BIOS resources.

Thanks.

My Inspiron E1705 (newer generation with the Core2 processor (originally it came with a Core processor, which didn't support x64)) has the same issue; the chipset only supports 4GB, which results in that it cannot remap the hardware's memory requirements to above the 4GB point, and the OS (XP x64 in the past and Win7 UE x64 now) only sees 3.4GB on my laptop.