"Cannot read configuration file" when running ASP.NET app

I recently decided to move all my VS projects to a dropbox folder so i don't have to carry my USB drive around all the time. I just copied all contents into the dropbox folder but when I run one of my ASP.NET projects, I get an HTTP error 500.19:

Module IIS Web Core
Notification Unknown
Handler Not yet determined
Error Code 0x80070003
Config Error Cannot read configuration file
Config File \?\I:\Documents\Schule\Praktikum\IHK-Projekt\WerIstWo\WerIstWo\web.config

I think it still looks for the config file in my usb drive, which I assigned the drive letter I:. How do I change this so it will my local the Dropbox directory with drive letter C:? What happens if I install Dropbox on another machine on D: drive? Will I get the same error?

Thanks for any help!