What is the I-PIN? The I-Pin is a kind of alternative to using your ARC on every website. This is extremely useful for foreigners as many Korean websites don't feature specific sign-up pages for foreigners. The process is fairly simple first you'll make an I-PIN using your ARC but then on subsequent websites you can use the I-PIN to sign-up. It is the same sign-up page that the regular Koreans use. There are actually several companies that provide I-PINs. As a foreigner there is one we should use.
To make your I-PIN head over to 공공I-PIN. They're a foreigner friendly I-PIN company. The other companies require additional verification, a cell phone, bank certificate, etc. The English sign-up for this requires nothing beyond your ARC. The page is entirely in English. So I don't need to walk you through this. To get you started though look towards the bottom for "Getting public I-PIN". Enter your info and within a short time you'll have yourself an I-PIN. There is some enjoyable konglish on the page, but it is still pretty straightforward.
Now, when you want to go sign-up for a site that doesn't have a foreigner sign-up page, look for the I-PIN option. Here is where your mileage will vary. On some sites this works perfectly fine, like Windyzone, but other sites will kick back a name error. Nexon and Netmarble currently do this for me. However, I spoke to another foreigner who was able to sign-up successfully for Netmarble. I've got e-mails going to them to figure out what the problem is. I've sent an e-mail to Nexon asking them about it, but they haven't gotten back to me yet. I've also asked 공공I-PIN about letting foreigners set a "Korean" name that could be passed to the site as verified so that it wouldn't break their forms. Also no answer on that one yet.
The I-PIN has a lot of use just beyond games. It will also help you sign-up for other sites. I just used it to sign-up for the E-mart website. They do have a foreign sign-up but the I-PIN worked just as snazzy. If you have issues on individual pages you might try finding their customer service center and attempting to contact them. Some of them respond quite well to English e-mails. Look for their 고객센터. Usually upper right. Once there you might dig around for an option that looks like "1:1". This is what they use to refer to e-mail help. Most sites let you access this logged out but something, like Nexon, don't. Don't ask me how you're supposed to get help if you can't register. Netmarble will not respond to English e-mails.
While this is useful for convenience on some sites, it is a necessity on other sites. Windyzone is one of those sites and so is Netmarble. If you try to sign-up for Netmarble, let me know if it works or not. Also let me know how many letters your English name is.