I'd like to go through the Vocaloid 2 import feature for Vocaloid 4, I'll be using the 'Tonio' sound bank in this example.
First thing is we'll want to download the Yamaha Vocaloid 2 import tool, which Zero-G does have available for download: http://www.zero-g.name/VOCALOID2_LibImportTool_2_0_1_Setup.exe.zip (if that link ever goes down, I'll upload the tool here).
If you haven't already, install the Vocaloid 2 Tonio package (along with the Vocaloid 2 Editor, you can skip installing the VSTi though). Once installed ensure you have activated the Vocaloid.
Launch the Vocaloid 2 Import tool and select the corresponding Vocaloid from its activation location, in this instance I have it activated against my SSD and not my network card:
The caveat here is that you'll need to get the special import code. Yamaha USED to have a server that would automatically generate these, but since they took it down, Zero-G will have to be contacted to get the code on your behalf. According to Zero-G they still support this: http://www.zero-g.co.uk/store/vocaloid-support-w25.php
In the event that you don't want to go through that process, the Vocaloid 2 editor does work fine under Windows 7 and a 4K display, I'm not sure about Windows 10.