You can follow instruction from this how to and set D: drive as new location to save apps, documents.

https://www.howtogeek.com/245706/how-to-change-the-default-hard-drive-for-saving-documents-and-apps-in-windows-10/

I keep ONLY OS and files FORCED to go onto the C: drive on it, and some others I want to have if I should need to RESTORE my C: for any reason (I make periodic back ups of all my drives). Everything else goes on my other drives.

C: needs some free space also to install Windows Updates, so I generally leave a lot on C:.

So, when you go to install a program, it generally will default to C:\xxxxx for the location to install it. Select 'Browse' or maybe even 'Custom' and you'll get a list of drives and folders... select D:, and usually the folder will not change, but I'd suggest you select the D: drive and add a new folder you want it to go into changing the 'New Folder' name. Those you do want on the C:, you would not do this.

@ispalten​ So what is the D drive even for? When I google it, I only find answers that say it's a partition of the C drive. But on these XPS machines, it's a separate drive from C, so all these answers are irrelevant. 

I read one comment saying D holds restore points. But my restore points are on the C drive and the D drive is completely empty. So I'm wondering if it's there for some purpose I don't know about? Or are they just intended for extra storage?

@strux​ 

Treat the D:\ drive just like an EXTERNAL drive... it is FOR storage of anything you don't want on C: drive (saving space on that drive for OS related files AND data, like where programs put items into the Documents folder on C: and specific USER folder related items).

Did you ENABLE Restore Points?

See https://www.dell.com/support/kbdoc/en-ed/000148025/how-to-run-system-restore-on-windows-8-1-on-your-dell-pc

Same for W11 as well as it is stated in the link above.

Using the 2nd drive, like I said, just like you would use an External, but use it for everything BUT the OS files.

Some links to read:

https://www.lifewire.com/use-two-hard-drives-in-one-computer-5222733

https://www.diskpart.com/articles/install-programs-on-second-hard-drive-0725.html

One thing I do do, put the SWAPFILE.SYS file on the Hard drive, NOT the SSD. SSD's have limited writes (may never reach it though) and unless you have LOW RAM depending on what you do, you may never write to it.

See https://www.windowscentral.com/how-move-virtual-memory-different-drive-windows-10 and yes, IF you are swapping due to low RAM it can take some seconds more to restore needed files, but it should be RARE and the time difference, minimal.

I have 32GB of RAM and I can't RECALL the last time I swapped Memory, even with 16GB's.

Easy to do, just follow the arrows,... I have 4 drives and use L: for the Swap file:

@ispalten​ Adobe apps need to go on SSD, though. I do a lot of intensive photo and sometimes video editing. 

It's a good practice to keep your software and your personal folders (i.e., Desktop, Documents, Downloads, Music, Pictures, Videos) on separate partitions. It isn't necessary to do this, but it does have advantages.

1- You can backup your software and your personal folders separately. If they are on the same partition, and you have to restore a backup, your personal folders will go back in time to when the backup was made.

2- You can backup your software and your personal folders on different schedules, to suit your workflow. You can also backup with different applications, if you wish.

3- If your C drive becomes inaccessible for some reason, or if you have to reset your computer, your personal folders aren't affected.

When you are stating the answer are not relevant, not sure of which answer you are expecting but the bottom line is the HDD is a storage device.  In Dell systems with a second HDD, it is formatted as a DATA drive and users can use it for any preference purposes.

My previous post confirmed to your inquiry that you can put files, apps onto the HDD with a proper procedure which would not cause issue or messing anything up. 

@strux​ 

That is fine, as long as you have enough space on C:.

After I posted how to do it, I checked my C: drive and I still have a SWAPFILE.SYS on it and my L: drive. I can NOT delete it 'easily' from C:. It is hard wired there on W11, so I have both it seems to be used.

Been like that for some time, probably a W11 change and I never noticed it until now.

@Chino de Oro​ Sorry, I meant the answers I found when *googling* were irrelevant, because most of them refer to one partitioned drive. I didn't know our 8940s have two separate drives. (Learned that from a discussion somewhere else where someone tried to allocate space from D to C, and he was told the 8940s have 2 drives, so all he did was remove space from D). Glad I didn't try that! 

xps 8940 costco only has 500 on the c - you have to switch all your new content to be saved to Data so switch it in system storage  System - then storage - advanced storage settings - where new content is saved  then adjust them all to data. you might have to uninstall programs you have on c and then reinstall on data like any gaming or graphics programs- I would also upgrade the ram with the two empty slots with this model

Crucial RAM 64GB Kit (2x32GB) DDR4 3200MHz CL22 (or 2933MHz or 2666MHz) Desktop Memory CT2K32G4DFD832A

https://www.amazon.com/dp/B07ZLD6Q1G?ref=ppx_yo2ov_dt_b_product_details&th=1

@kingofsneakers​ I already ordered the 16 GB kit for my two remaining slots, because apparently it's not good to mix & match. (Currently have two 16 GB cards).

I don't need to move everything. Just wondering if I could store a few things on the D drive to free up my SSD drive a little. 

You can map your my documents folder and so forth to D and windows will auto-move the files there. You can also install apps and programs on it.  I use the NVME for OS, SSD ( I installed myself) for programs that require an SSD, and then just use the HDD for mapping my documents and apps that don't require fast speed.