Make sure you have show hidden and show system files and folders enabled. You may also not have installed to the drive you had intended to.
I would also note that I know someone who installed a pirate version and i could not find his community folder. Fortunately, he liked it so much, that he has now paid for a proper version (he was partly persuaded by World Update 3 as well). Not something I would condone, but had a good outcome (well, I paid for it for him TBH as I owed him a favour).