I have a Compaq Presario Desktop PC (not sure about the exact model) I was wondering if i could upgrade some of the insides?

(It's the very first computer i ever got, as of now my mom just uses it for work related stuff. I have upgraded to a MacBook air, but it would be nice to be able to play some games<GTA, Witcher 3, skyrim, fortnite, MineCraft, & well others> or at least it would be nice for it to be faster than it is now so its not such a pain for my mom to use it)
-Case is a mid size ATX
-AMD athlon 64 processor 3500+
-991 mhz 488 mb of ram
-Mother board, Hard Drive & Power Supply is unknown at the moment
-SuperMulti 16X DVD Ram (i think)
-9-in-1 multimedia card reader
-Front I/O ports USB: 2 & Headphone: 1
-Back I/O ports PS/2 mouse (green), RJ-45 Network (LAN), Audio: Line Out (lime), Audio: Line In (light blue), Audio: Microphone (pink), USB 2.0: 4, Video Graphics Adapter, PS/2 keyboard (purple)

I'd like to put a new Mother Board, CPU, Ram, & Hard Drive
I'd like to keep the Case, DVD RAM, 9 In 1 Card Reader, & Power Supply if possible.

Does anyone know if it could be done? Could you suggest any hardware? Should i just replace the whole computer(don't really want to do that but if i have to i will)? I would really appreciate feed back good or bad, so don't hold back state your opinion/thoughts.

Compaq has been using the Presario line for nearly two decades. Not enough information to know whether you have a six month old Presario that could be tweaked for a couple hundred dollars or a 15 year one that is worthless. Would need a model number or some kinds of specs (processor, speed. Ram, video card, system board, etc.) to make any guess.

Not worth doing, but if you must you might be able to increase the amount of RAM you have there for better performance.