Solved

Ok, I wanted to find out which harddrive it's creating errors, as I am beginning to suspect it wasn't the RAID1 configuration that is getting the short end of the stick. So, I restarted and opened up "My Computer", thinking it was one of the other drives creating problems, cascading into Explorer and thus giving headaches for the software as they'd meet a dead end if Explorer started to hang up.

I looked at the G-drive (I have C and D for the RAID1, G and H for extra space), and began a Control of the disk. It started up fine. In the "My Computer" it showed the total size and how much free space there was. After a while the Control (I set it to "Repair automatically" and "Search and attempt to fix damaged sectors") stopped and I looked in "My Computer", and the Total Size and Free Space was blank for drive G!

This is the culprit. The error starts with a bad sector in drive G -> which causes Explorer to hang up IF you use a search function of the drive in question. Then this leads to software which attempts to use Explorer to search for files (eg. jpg's) will hang. Ok, the solution isn't then to send the machine to Dell, but to pull out the G-drive, reboot and see if the problems goes away.

Incidentally I bought two identical drives, both 1TB Barracuda's.

To see what would happen, I did the same test on drive H, by using a Control on the drive. The drive works perfectly, but because the G-drive hangs, I probably have to do a cold shut-down. Then pull it out.

Done. It was the G-drive. Then I determined to find the cause. The drive's firmware version was one that was suspect, so they recommended to flash the firmware to a newer version.  So, problem solved, for now.