The Dimension 3100/E310 is too old and too slow and only takes 2 gigs of ram.
Socket LGA775, Intel 915GV
2 Dual Channel DIMM Support for DDR2, 2 GB MAX system memory, 2 PCI Slots
1 PCIe x 1, Integrated 10/100 Lan, Onboard Sound, 2 Serial ATA Hard Disk Connectors
1 ATA-66/100/133 IDE Hard Disk Connector, One Floppy Connector, 4+2 USB 2.0 Ports
A better choice at a minimum would be Optiplex GX620
There are no windows 7 specific drivers for the GX620 up to GX760 supports all windows from Msdos all the way thru Windows 10.
You may or not need to install drivers separately to run Win 7 on the D3100.
Run the Windows 7 Upgrade Advisor (free from Microsoft) and see what it says. Many drivers may already be built into Win 7. If the Advisor flags something as potentially a problem, go to the website for that piece of hardware (eg, video card) and see if they offer a Win 7 driver for your specific hardware.
Yes, the D3100 is old with only 2 GB of RAM, but Microsoft will be supporting Win 7 until Jan-2020, so you might squeeze another ~2 years of use out of this PC.
Forum Member since 2004
I am not a Dell employee
People have been able to run windows 7 on 1Ghz Pentium 3's
I personally have used windows 7 on a Compaq EVO D510 SFF which has an even older Pentium 4 (socket 478) with 2 GB of DDR SDRAM
It's not fast but it's usable boot up only take 2 minutes and it can be used as web browsing appliance.
And since the Dimension 3100 had Prescott Pentium 4's (LGA 775) you could run windows 10 on it as these were amongst intel's first processors to be NX bit capable
In my old Compaq, the windows XP drivers worked perfectly on windows 7 so use those they should work fine if not use this guide to force them to install.
I do not work for dell. I am also a user.