Manel, it seem's Intel has changed it, in December it allowed me to download using that utility. Now it throws that message while doing an auto-check. I have the version '15.33.30.3958' which is of last year October. Looking at their website it does seem, there is an update of January 2015, I haven't tried that one yet but the previous one is running fine so far, i'll give it a go this week to see how it is, quite tempting to try the new one. If you wan't go for the manual way, as it seems since they changed, that's the only way so far available, and seeing Asus won't update anything for us on their official page other then Bios this should be the only way, ofcourse if it doesn't work out you can always roll-back to the driver from Asus.
Intel GFX Drivers for Z3700 Processor series,
https://downloadcenter.intel.com/Sea...ng&ProdId=3845
Btw, I did notice from the screenshot you posted, your 'Action Center' has some drivers/issues/pending to be installed/maintained, you might wanna go and fix those, otherwise it might create other issues for you later on. It's the Flag Icon 2015-02-19 19_29_05-Optimize T100 for gaming - Page 2.png, next to your battery, round circle normally recommends driver updates or some maintenance tasks which needs to be done, a simple flag means no issues, keep an eye on it from time to time, the hover of mouse on it usually gives an overview of what it is.
And thank's again for the check, I have updated my previous post with these details to help new users.