You can safely delete the .sdf file and ipch folder but you can also stop VS from putting those files in the project folder in the first place. (Useful if you have your source in a SVN or other synchronised folder, or if you store your project on a small volume like a USB stick or SSD and you don't want those large files stored in the same folder)
Go to Tools -> Options -> Text Editor -> C/C++ -> Advanced
In the "Fallback Location", set "Always Use Fallback Location" to True and "Do Not Warn If Fallback Location Used" to True. In "Fallback Location" you can either put a path like C:\Temp or if you leave it blank then VS will use the temporary directory in your AppData folder.
