Had a pc with pentium e5500 and ati hd 3850 with 2gb ram
It ran csgo fine in 2013,had like 100fps.
I used the pc once when my main one was in service and it took like 10secs before ANYTHING, even notepad opened.
In 2017 I had 40fps with the same system and settings.
Then my main pc came back from service and i used it for like 2 morr months and suddenly after an update in cs i was getting like 200fps which is low cuz i have 144hz and it was unstable, i had to replace i5 4460s with i7 4790 and now I have 300fps in all scenarios.
Everytime i did clean os install but once u have a shitty pc it doess help very little