Firstly, you don't say if the 320Gb disk is SSD as well, if it is then we are probably dealing with an ssd issue - of which I know precisely nothing, but there are a couple of posts on the forum that might help I don't know:viewtopic.php?f=90&t=101810&p=578163viewtopic.php?f=90&t=79503#p461796
Otherwise the first thing to try is to open the 'disks' program from the menu, select the correct disk, then click on the cog icon on the top right of the gui. This will open a 'Smart Data' window with the latest 'Smart Attributes' listing many properties of the drive. Any faults listed there? You can start a new self-test from that window as well to get up to the minute information.
Another thing you can do, which might help those more technically minded than me, is to prepare a system report and post it here. Open the 'System Information' program from the menu, click on 'generate report' then narrow it down a bit by expanding 'Computer' and removing 'Boots', 'Display' and 'Users' also uncheck 'Network' and 'Benchmarks' as none of these are relevant. Then click on 'Generate', choose a place to save the results then upload the file to the forum.
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