Yes, you can upgrade the hard drive. Even though Acronis True Image Home Edition 2014 says that it supports windows 8, 8.1, it only supports backing up your data but not hard drive cloning.
Note: All the ASUS Transformers have the same thing in common. The Tablet portion holds all of the hardware. With this being said, if you want to upgrade the memory, now is the time to do it.
1st: Use Acronis TIH 2014 Edition to create your data backup onto a larger flash drive, not the one you'll be using with the OS if it's on a USB flash drive. Next, open up the tablet by removing the screen bezel & removing all the screws. [You Tube the "How To" disassemble video [your version/model number.] Once you have the lid removed, remove the hard drive for the upgrade. Also the memory too if it only has 1gb of rm
2nd: Have you Windows 8 Operating System Disc, or call ASUS Tech Support to see if they will email you with the windows OS downloadable version so you can put it on a flash drive. At any rate, which ever version you can get, the BIOS will see that you're using the correct OS on Disc or Flash Drive. Once you have windows installed, use your data backup to reinstall the data since you get things like office home & student. The hard drive should be around $37.99-$59.99 but remember, if you have it open, see if you can find the 256gb hard drive since the solid state drives all use about the same wattage which should match the battery life. I've been getting 256gb SSD's for under $79.00. I am going to use the 256 SSD's because of the resale value
***Please note: If you can only use an operating system disc, make sure to have a usb external optical drive.***
Now if you have 2 different BIOS Settings, use the open version if you would like to try windows 7. I'll be upgrading 2 of these tablet/notebooks with larger hard drives because the original price of these little guys are pretty expensive, installing large hard drive will bring in a lot more money.
Now about the Transformers, yes there are 2 different models. The older models can't be upgraded but like the other posts, if you can upgrade the hard drive to a SSD then you're all set. It just takes a while to get it completed. Enjoy & do it because the 32gb or 64gb models need to be changed since there's not enough room to do what you should be able to do.
The reasons I purchased the ASUS Transformers is because I am not going to buy a Surface with a $500 price tag when you can buy 2-4 depending if they're refurbished or NIB...