[jimmydorry]

Yes and no.

For a contract to be binding, there has to be consideration [1] from both parties.

[1]: https://www.australiancontractlaw.com/contractlaw/formation-...

>Consideration is the price that is asked by the promisor in exchange for their promise – the price for a promise.

>In many jurisdictions consideration is not an essential element of a contract – it is sufficient that parties have reached a binding agreement. However, the common law requires that (subject to limited exceptioins), for an agreement to be binding, the promisee (or promisees) must provide consideration (payment of some kind) for the promise they have received.

>As a result, gratuitous promises are generally not enforceable.

[jon-wood]

Consideration doesn't have to be monetary, in the case of the Windows EULA Microsoft are receiving someone who may or may not go on to buy other Microsoft products, while the end-user is receiving a copy of Windows they can use for the period of the trial.