I only just stumbled upon this thread, but the key piece of information in your original post to me is:
I have all the media files on 2 External Seagate ( 1 x 2TB, 1 x 4Tb) drives run on USB 3 from 2 ports on the PC
External USB drives are going to be quite slow, especially when used in tandem. There are some recommendations you should review in the Troubleshooting Guide:
http://wiki.jriver.com/index.php/Troubleshooting_Guide#Disks_and_LocationsOne thing, in particular that might help is
an option described in the Troubleshooting Network and Slow Disks sub-page. However, read through the whole thing, as there are other points in there that could be applicable to you (especially if you have your Library files stored on those external disks). Also, just to explain something: You mentioned it was being used on a USB3 port, but you didn't mention if the disk itself is a USB3 model. Even assuming it is, just because the disk supports USB3 does NOT mean it performs like a high-performance internal SATA disk. The bus is faster, but there are a lot of other factors in how a disk performs (and external disks from most vendors can be assumed to be the crappiest disks they make, in many cases). Another consideration is that you're using two of them. Obviously they're plugged into two separate ports on your computer, but these two ports are
almost certainly "split internally" and not on separate controllers. This can further slow disk access when both are being actively used simultaneously.
Also, as noted in the guide, when MC is building thumbnails, it'll thrash the disks pretty hard. You may be able to improve performance without doing much else by simply pre-building thumbnails:
Tools > Options > Tree & View > Thumbnails > Build missing thumbnailsThis is the most likely culprit for why you are seeing a difference when you add video. MC has to work quite hard to build the thumbnails for video views, and this involves a LOT of disk access to the media file location itself. Your disks are slow, so this will perform poorly until it is done. For the record, though, I have a huge video library. There is nothing inherent to the size of the Library (not on the scale you're discussing anyway) that limits performance. MC can track libraries with a half-million assets with relative ease.
Disk access can also be slowed by Anti-Virus application behavior, and if you're already on a slow disk, this can have a substantial performance impact. Review this as well and exclude the MC processes and at least the folder for your Library's directory:
http://wiki.jriver.com/index.php/Troubleshooting_Solutions#Tame_Your_Anti-VirusAnd, lastly, 4GB of RAM is about the bare minimum I'd use on a Windows 8 system. MC is typically pretty efficient in using RAM, so I doubt that is specifically your issue (though other applications could be gobbling it up too, making the amount available to MC much lower). But, RAM is cheap, and it might be worth upgrading just because.
