If so, try 99 bucks. It's awful but I gave away a 2008 HP D4999T with Windows 10 on an 120GB SSD ( the only way I found it to run fast today.) It included the mouse, keyboard and display and the reason I parted with it was that it had its day and that day passed.
There is some issue with selling a PC that the buyer may want me to warranty the machine which you can't do on old gear. So I let it go.
I lucked into a new to me Chromebook 15 inch laptop for under 99 bucks so for old gear, complete that is not a gaming rig, my answer is 99 bucks. Or a Benjamin.
I'm a little short on cash and have an outdated(windows vista) pc, and i have no idea what i can sell this for and i dont want to get screwed by the person i sell it to,
Its ultimately useless for my pc needs.
Specs:
Operating system: Windows vista premium
Made by dell,
Model: Inspiron 530S
Processor: Intel(R) Pentium(R) Du CPU E2200 @ 2.20 GHz
Memory(RAM): 3.00 GB
32-bit operating system
Idk if you guys need any other information , (and the computer runs very smooth. Just cant handle a lot, starts up quickly too,)
Where should i sell this, and what price estimates can you give me?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic