Some very hard to diagnose crashes over the years have been mixed RAM. That is, unless you have no troubles, you don't mix. If it you have troubles and find mixed RAM you correct that along with (if it's old) do a deep cleaning of the heatsinks, fans and replace thermal compounds.
Some of this old gear won't work any longer so don't invest in these.
If you want, share machine details with the make, model PSU as well as a Web Speccy report.
Read how at https://www.piriform.com/docs/speccy/using-speccy/publishing-a-speccy-profile-to-the-web
So I have just began using an old computer again and for whatever reason, when i do certain things, such as watch videos, play games or visit certain websites it reboots, whenever it reboots it does it as if i normally would have rebooted it, along with that when i install more ram it crashes almost instantly, I'm unsure what is causing the problem and any help would be much appreciated
CPU : Intel Core 2 Duo E7500
Graphics card : Intel Q45/Q43 Express Chipset
Ram : 4GBS DDR3
If you need any other info please tell me and I will respond ! thanks for the help