If you transfer files to the USB key that are infected with viruses, and you move them to the host, then yes, you are risking for the host to get infected.
You have to replace they keyboard in order to solve the issue.
Keyboards are generally not difficult to replace. Find out if it's under warranty so you can get a replacement. If not, you'll have to buy a keyboard.
Both are good options. The Dell XPS 15 looks way better hands down, but doesn't have numpad like the Lenovo.
I would personally take the Dell because of the sleek and bezeless design. Looks more modern per say. Can't go wrong with either or though.
It's either your PSU or motherboard more than likely.
Page 51 of the manual here says it's your PSU/mobo:
http://downloads.dell.com/manuals/all-products/esuprt_desktop/esuprt_dimension_desktops/dimension-e521_service%20manual_en-us.pdf
Install the Hyper-V feature/role on your Windows 10 machine. Within Hyper-V manager, hit "edit" disk, select your .vhdx file, then convert it to .vhd, and voila.
This is all done through a wizard, so you don't have to use PowerShell.
Okay, it looks like the laptop is covered under warranty.
Contact Dell so you can troubleshoot the machine, and they can send replacement parts as needed.
You will need the company name of the service tag. This means wherever you got it from, or the company that purchased it.
Do you have the different model names?
The motherboard service kit for that part # is XJK10
It's just really hard to pin point which models have that board #4DKNR if all the models for the 1558 show it as a valid part #.
Do you have the service tag of the unit? It would be much easier to find that way.
Looks like there are 3 models for the Studio 1558, and all of them use the part # 4DKNR for the motherboard as a valid compatible part.
How did you disable the integrated graphics? You might have issues if you did it through device manager.
Ideally, the way you would disable the integrated graphic chip from a hardware level is by utilizing Nvidia Optimus technology. This is a feature that you would switch on/off in the system...