I am having a real hard time with this and have looked all over the internet for a possible answer.

I have a rough idea on how to make a form for a website using HTML, PHP or whatever coding process needs using the only thing I can't seem to find information is an answer for this scenario.

I need to make it so in order to download a file someone has to fill in a form giving their details to the company. I don't want a login system as it won't fit in with the website but I need someway of blocking access to the download without filling in the form.

Any ideas?