I have always wondered about the legality of the Eula. How can it be enforced? Is it a legal contract? And is it valid in all countries? Not all countries have identical laws...
I remember Psystar attacked the Mac OS X Eula. And in Germany, a company started selling PCs with Mac OS X preinstalled; their argument for this was that the Eula was invalid in that country.
Some courts in the U.S. have upheld shrinkwrap license agreements. See particularly ProCD v. Zeidenberg and more generally, Wikipedia's section on EULA enforceability. This covers how the DMCA may apply, for example.
In the end, though, you'll find that EULAs are sometimes deemed to be enforceable and sometimes not.
EULAs are not per se invalid in Germany.
however, a German court held that they are ONLY THEN legally binding if they have been agreed to prior to the purchase. the folks at PearC, the company selling Mac clones in Germany are founding their claims of legality on this 'loophole'.
The bottom line is big software company can afford more billable lawyer hours than you can. Call me a cynic, but I believe in the golden rule, "those with the gold make the rules". You might eventually get a judge / jury to rule in your favor, but you would go completely bankrupt in the process.
The only silver lining, we out number them and they can't afford to catch and try everyone. As long as you don't bring attention to yourself, like responding to a question on a popular website, they shouldn't notice you.
Some EULAs are in fact invalid in some countries. I think this is a case for most US EULAs used in EU. US legal system has some resemblence to UK legal system, but EU legal system is in fact a mix of few totally different ideas how law should look like, and is quite different from US.
In most cases, it's not enforceable
In the software world (market), I think we pretty much live on a honest system.
For some parts of the world, piracy is as high as 90% or above. People don't really care or are unaware of software license at all, not to mention EULA.
For some developed countries, people pay more attention and respect to properly licensed software, but still, we have an attitude of "I pay for the software so I am fine with it." Nobody is actually reading the content of an EULA.
Exception
The only times when an EULA is enforced would be in a corporate environment where a large number of licenses are compromised and catch the attention of the owner (e.g. MSFT). In such case, a team from the law enforcement body will raid an office and... you can imagine.
In theory, the EULA is enforceable in most countries (although I would really only know about Australia) as it is a contract that you have agreed to. However, when it comes down to it, if a EULA is challenged or a person is sued or charged for breaking a EULA, it always comes down to the courts to decided whether or not what the person did was illegal or not.
Just to be on the safe side, I would recommend you follow them.
Legalities dealing with different countries aside...
I would say because you are using someone elses product. It is their property and they are just licensing you rights to use for it's intended purpose and nothing else. You agree to not use the product for other purposes, diassembly, use code, copy ideas/pictures/exact layout etc.
They have all the legality of private land parking signs threatening to clamp you if you park on their land. Very shaky ground legally and probably wouldn't stand up in court but the threat of them is enough.
If you understand the Dutch language then De (on)geldighed van EULA’s (gastpost) will try to explain it from an European view. If you can't read Dutch, then Google Translate might still make it readable.
But in short: it depends on the situation.
What about the right to do reverse engineering provided as fair use in copyright law, you bought the product you have that right. Then you can deny to accept the EULA, which by no means would take from you the rights acquired when you bought the product to reverse engineer it. So you reverse engineer it to take away the EULA in the installer, and then proceed using it normally without accepting the EULA. Isn't this valid?