I'm interested in purchasing a dedicated server. I've honed in on the one that I want - http://www.hetzner.de/en/hosting/produkte_rootserver/eq4 but I really want to use a windows OS.
Though Hetzner does offer a windows OS, the fees are very steep - 15Euro per month!
Would it be a problem to install Win 7 Ultimate, for example?
Bear with me if I'm insane - I don't know much about OSes.
You may wish to consider Amazon EC2 for hosting a Windows instance for you. As others here agree, it only really makes sense to run an instance of Windows Server. If you pay for 3 years up front, you can run a Windows Server on EC2 for as little as $2.28/mth (USD).
There are, of course, other Virtual Private Server (VPS) services available. Though most that I've payed attention to were for Linux machines (which I believe must be simpler & cheaper to virtualize in an automated way).
This train-wreck of a website, as another example, provides a Windows 2K8 Server VPS service for $2.50/mth
May I ask what you want your server to do?
Well, Windows 7 is a client OS, if you want a windows server, you are better off with a windows 2008. And honnestly I don't think hetzner has an option to install windows 7. What you can do, is install a base OS with Xen and virtualise a windows 7 on it to see if it fullfills your needs, if not you can still buy your own w2k8 license and virtualise that one instead. (if you could get the license than hetzner cheaper ofcourse).
That is a hosted server, so you can't install anything you want on it: your hosting provider will manage operating system setup and configuration, and then you will put your applications (whatever they are) on it. So it's their right to choose which O.S. you are allowed to use, and if they are not completely insane, they are definitely not going to offer Windows 7 (or any other client O.S.) as an option.
If that was your server, you could install anything you wanted on it; but of course buying, installing and managing your server would have a completely different cost than renting a hosted one. And, even if that was the case, I'd anyway strongly advise you against loading a client O.S. on it. They are simply not designed for this kind of job.
That said, € 15 per month makes € 180 per year. As per this page, a single license of Windows Server 2008 R2 Standard Edition costs more than a thousand dollars, and a Windows server is very unlikely to keep using the same O.S. for more than five years, so this offer would cost you roughly the same as buying your own Windows Server license... but you will not have to manage it on your own. Which, as you "don't know much about OSes", may very well be a big plus.
