If you are stuck on the name brand (MSOffice), and find it for 150 or less, LEGAL, buy it. The Home and Student version has almost everything the Standard Suite does, except for Publisher. You can find it at Amazon or Educational Resources.
STICK WITH "NAME" SOURCES for your software purchases.
Note please, I'm not dissing MSOffice. I use it for some work stuff myself. However --
Open Office does pretty much everything that Office does, and both opens and saves MS Office files. And, it's free. Looks a lot like Office. Some of the buttons are labelled different, or in a different place.
To follow up on the OEM comment upthread. Trial or full doesn't make a difference. If the license sticker says it is an OEM version, it is only valid on THAT machine.
And, while you could delete the trial version and remove all traces of it from the computer's registry, then redownload a new trial, it really isn't worth the hassle and risk of hosing your machine.