Can I remove a DVD Drive and use it's SATA for a 2nd Hard Drive?

If it was possible, Raid will only create a 4.6 GB drive since that is the largest disk you can put into the DVD drive.
No matter how big your hard drive is. Raid will only use the smallest drive as its total.
I suggest you buy another hard drive equal in size to the one you have.

If the dvddrive is connected to a sata connector, I expect you could use it for an ssd instead provided you can find somewhere to fit it in.

Can't comment on raid because I never use it.

You should be able to remove the current DVD or other device that you no longer have a use for, the sata will accept any Hard drive that uses the correct attachment system, both physical hardware connection and software must be compatible and it makes good sense to match the original spec as as stated you will be limited by the smallest drive as to the final raid that is possible, I'm sure that @Brink has a full range of tutorials to cover your hardware on the forum

I have ran Raid systems for many years for my own systems an also for many clients and employers, I do not see the need for Raid in my current systems and there is a general reduction of it in industry, apart from data centres due to the availability of relatively cheap large drives these days, this does not of course remove the validity of raid as a solution to many users needs

https://www.sevenforums.com/gtsearch...a.x=12&sa.y=10

I have not had any form of Removable Optical disk drive in my systems for many years I have a twin 16GB setup in my desktop, for my data I have not set those up in a raid as I find them big enough for my needs as they are, . plus I have several external drive cases for backups and occasional use data. I also have an external Blu Ray RW drive for dealing with the occasional optical discs I need to access My OS is on an NVME drive and my optical disk use is replaced by external sticks or drives

HDD is dead tech.
RAID 0 was to achieve relative high speed. A SSD is almost 6 times faster than a HDD and will be 3 times faster than RAID 0 on HDDs.
As SIW2 suggested, install a SSD for OS and programs and use the HDD for data.
If your ODD is the kind that comes on laptops, remove the ODD and install a HDD caddy with the SSD on it.
There are two types: 9.5 mm and 12.7mm ODD. Find out witch one you have.

HDD HD Caddy Case for 12.7mm Universal Laptop CD Bay

HDD HD Caddy Case for 9.5mm Universal Laptop CD Bay

I am not sure if the sata port for the dvd is sata2 on that mobo. Looks like there are two blue and one white.

It might tell you in the service guide

http://h10032.www1.hp.com/ctg/Manual/c03821564.pdf