Multiple problems on Windows 8 (explorer.exe crashing; file copying stops; multiple instances of Task Manager and Skype)

Multiple problems on Windows 8 (explorer.exe crashing; file copying stops; multiple instances of Task Manager and Skype)

I've been having some problems on my MSI GX620 running Windows 8.
Sometimes when I do something in File Explorer (like press delete to delete file, or right click on a file) the File Explorer window stops responding. Soon after that the taskbar stops working (but I don't get the "busy" mouse cursor). After a while explorer.exe decides to restart, but it never starts again properly. I just see the background of the taskbar and nothing else.
Now I have two explorer.exe processes in the Task Manager. One of them is not responding. When I end the process that is responding, the taskbar background disappears. When I try to end the explorer.exe that is responding I get an error message that says:
Unable to terminate process. The operation could not be completed. Access is denied.
(I am the administrator and only user of this computer)
To fix this problem I have to restart my computer.



Another problem is that I downloaded some mkv videos (around 1.4GB) and when I try to copy some of them from my D: drive to an external hard drive, the copying stops at some point (not for all videos). When I try to copy the same video again, it stops copying at the same point. By "stops copying" I mean speed goes down to 0 bytes/second.



And the third problem is something to do with application instances. Before, if I tried to open the Task Manager and it didn't open immediately (due to my computer being slow at the time) I would try opening again. When the Task Manager did open, I would get one instance of it. Now, when I do the same thing, I get multiple instances of it.
And the same with Skype. When I open it the first time it just logs on, and then doesn't show the Skype window (even when I double-click on the Skype icon in the taskbar). To get the Skype window. I run Skype again (which opens another instance of Skype). Skype then gives me an error that I am already logged on to Skype on this computer. Then I right-click > quit on the not-logged-on Skype icon in the taskbar. After that I double-click on the logged-on Skype icon in the taskbar and it opens.
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I don't know if these problems are related, but they all did start appearing at the same time.
Any help to fix this would be appreciated.



Here are the results of chkdsk:
Microsoft Windows [Version 6.2.9200]
(c) 2012 Microsoft Corporation. All rights reserved.

C:\Windows\system32>chkdsk /f
The type of the file system is NTFS.
Cannot lock current drive.

Chkdsk cannot run because the volume is in use by another
process.  Would you like to schedule this volume to be
checked the next time the system restarts? (Y/N) n

C:\Windows\system32>chkdsk
The type of the file system is NTFS.
Volume label is Windows 8.

WARNING!  F parameter not specified.
Running CHKDSK in read-only mode.

CHKDSK is verifying files (stage 1 of 3)...
  469504 file records processed.
    File verification completed.
  33297 large file records processed.
  0 bad file records processed.

CHKDSK is verifying indexes (stage 2 of 3)...
  621088 index entries processed.
Index verification completed.
CHKDSK is scanning unindexed files for reconnect to their original directory.
  1 unindexed files sca