Originally posted by Vintage:

Maybe Internet Explorer corrupts the Zip archive or something. Try using another browser, unless you already were using another browser. But if it keeps being annoying... The Steam version of Blender has the Blender Source Tools pre-installed, plus it also auto-updates.

Using chrome

Originally posted by Freddie:

When you click download does your browser give you an option to open the file or save as? If so click on Save As and then do the steps outlined above.

No the zip file just pops up

Originally posted by Freddie:

Are you trying to install the add-on? If so use the import add-on function.

To get to it:

1. Press (Ctrl+Alt+U) This takes you to User Preferences
   
2. Click on Add-ons tab
   
3. On the bottom, click on Install from File...
   
4. Browse to where you have the file and click on Install from File...

Thats my problem, I cant drag and drop my folder into my computer and whenever I try THAT error comes up, thank you for your support though. :)

! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\datamodel.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\export_smd.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\flex.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\GUI.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\import_smd.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\ordered_set.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\translations.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\update.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\utils.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: Unknown method in io_scene_valvesource\__init__.py
! C:\Users\Ronin\Downloads\blender_source_tools_2.5.2 (7).zip: No files to extract

When trying to download blender source tools and dragging/dropping the folder this error pops up, any help would be greatly appreciated!