Hello! I have 2xhdd: WD 1Tb 7200rpm sata/Seagate 500Gb 7200 sata, never had any troubles using them but today something odd happened. I installed Alan Wake AN (Steam) and when i clicked play it started the normal preinstalls as dx and etc and suddenly after that i heard my 2nd drive(seagate 500) kicking in and the pc rebooted, no hard reboots or etc just the normal windows way, after that i checked event log and nothing unusual. My win is up to date so i can't explain to myself. Those steam preinstalls don't require restart and never asked me for one.
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Have you tried reinstalling to see if it reoccurs? Before you do that, go into the game properties (via steam) and have it do a file integrity check to make sure it downloaded properly.
Just did this but none of the preinstalls started. The game starts instantly.