Is there a PCIe x1 slot available on the Dell T5820 PC ?

Thank you.

Supported Operating Systems Precision 5820

Yes, but you might be disappointed with it.  The raw version of it, Win7 SP1 on CD/DVD lacks some basic functions.  Almost all needed drivers would need to be manually downloaded, starting with chipset, graphics, and so on.  And as we know, MS cut off updates for Win7 for quite some time now.

If you have an SSD/HDD with Win7 on it that includes the updates, you would be in some luck and would just need the driver's.

Dell Precision 5820 Tower Owner's Manual online

#4 in the screengrab is a PCIe x16 slot wired as x1.  Card doesn't have to fill the slot in order to work as long as the notches line up.

Dear Mr. Bradthetechnut,

If we have a VP net board with a male socket like this, is it compatible with the PCIe x1 slot of the T5820 as you shared ?

Thank you.

I can't make guarantees from here, but it should work.  You can easily see the notch on the PCIe slot to line up the card.  Looks like the card might go in upside down.