Hi guys, so my friend bought Fallout 4 and started playing for a while without any problems until he started to lag only when in combat, from the task manager his cpu and memory are fine and both between 40%-70% but the matter is the hard disk which is 100% , I've found the problem but I need a solution, anyone with a tip? Any tip is usefull, thank you.

Check memory usage when that starts to happen. You may be running out of memory and it's swapping out data from HDD to ram.