At the time of writing, the SkyDrive client application on Windows does not support bandwidth throttling on uploads, so if you start uploading a large number of files, it will try to use all the available bandwidth, and this behaviour has an impact on other applications accessing the Internet.
A quick fix to this behaviour is:
- install a network traffic manager app, such as SeriousBit NetBalancer (I will use NetBalancer in this example)
- start SkyDrive app
- start NetBalancer, and look for the SkyDrive process (SkyDrive.exe), right-click to open the menu, and choose Upload Priority | Limit...