Why such slow download of windows support software?
You can download the Boot Camp Support Software directly from here (554 MB).

A workaround with instructions and link to download can be found here:


The download file is a .zip file. Double click it to uncompress it,  if it is not automatically uncompressed.
Double-click the Boot Camp5 folder.
Copy the entire contents of the .zip file to the root level of a USB flash drive or hard drive that is formatted with the FAT file system.
When running Windows, locate the Boot Camp folder on the USB media you created in Step 3 and double click to open it.
Double click on setup to start installing the Boot Camp Support Software.
When prompted to allow changes, click on Yes and follow the onscreen instructions.
Installation can take a few minutes. Don't interrupt the installation process. When installation is complete, click Finish in the dialog that appears.
A system restart dialog box appears.  Click Yes to complete the installation. 


For detailed information about Boot Camp, please visit this link.