Ever came across this annoying and mysterious issue on how the SharePoint 2007/2010 Multiple file upload control shows either "Drag and Drop" screen or a flat "checkbox screen where you can only bulk upload from a single folder" - If answer is YES then read on to solve the issue for good in terms of how to always see the "Drag and Drop" screen for multiple file upload.
Ensure that you are unable to see the Drag and Drop feature when you click on "Upload Multiple Files" in SharePoint. If you dont then take the following steps to resolve:
1) If you are using IE Browser, Click on Tools > Manage Add-ons and validate this add-on version "STSUpld.UploadCtl" - it it says 12.0.... then its the older version as it should say 14.0... You have found your PROBLEM!
2) To Resolve Step 1 version issue, Open Add/Remove Programs and Click on Microsoft SharePoint Designer 2010 and select "Change" option. When wizard opens up then select "Repair" option and let the Microsoft Wizard do the trick for you. Let the Repair process finish.
3) Close all browsers down and now launch IE and goto your favourite SharePoint document library when you want to upload multiple files and VOILA! - You should see the Multiple File Upload control show the Drag and Drop Wizard
NOTE - If you note in Step 1 that you cannot find the Add-on OR in Step 2 where your client computer does not have Microsoft SharePoint Designer 2010, then I recommend you do the following:
1) Free download and install Microsoft SharePoint Designer 2010 (64-bit here / 32-bit here)
2) Free download and install Microsoft Silverlight
3) Free download and upgrade browser to IE 9.0 (recommended only not mandatory)