I also had a problem to install it, this it how i fixed it:
1. Download the *.gadget file 2. Rename it to a Zip-File: Blue_Microsoft_Calendar_Gadget_by_rapha2.gadget.zip 3. Extract to: "Blue_Microsoft_Calendar_Gadget_by_rapha2.gadget" 4. Copy folder to: C:\Users\%YOUR_USER_NAME%\AppData\Local\Microsoft\Windows Sidebar\Gadgets\ 5. Maybe now its already to see under your gadgets 6. If not: go into the folder -> "Blue_Microsoft_Calendar_Gadget_by_rapha2.gadget" 7. There is folder named "en-US", make a copy of this folder 8. Rename this copy to your country code: For example Germany -> "de-DE"
Oh, one more thing about the white box - one way I've found to make it go away (temporarily) is to click the gadget (going to the monthly view), click any date other than the current one (bringing up the white page with that date on it), then click the blue (or orange, on the original gadget) corner to bring back today's date. The white box goes away for this session, but will return next time Sidebar is launched.
The white box around the calendar gadget (of which this blue calendar seems to be a clone) seems to be a common problem - happens in both Vista and Win7 with IE9 installed. It has been reported to Microsoft, but so far their response has been completely unhelpful.
Here's a thread that may someday contain something useful: [link]