Ah hell, just quit your job and move back in with Mom. :p

Install on surface and play with a VPN (HideMyA anyone?). If the IT uses software to track installs edit the registry for the control panel description to say something work related or ok to have (Office Toolbar 2). If their real jerks, you can run it off a USB, but you'll have to lower your graphics on the game and get a high quality USB drive or you will see game play lag. Also if your using the guest network that stuff is monitored way more than the physical LAN, plug up to a jack if at all possible.
But all of this is a non issue, if your playing P99 at work, the real problem is getting so involved that someone walks up to you and sees you playing a game when your working.

Probably depends more on what the ips the clients connecting to resolve to as to whether anyone notices.

Like others said, a lot depends on your particular job. Bringing your own device and using a phone tether is easily the safest way to do it. But you also have to consider the location of your desk, how visible your screen would be, etc. Lastly, knowing your company HR policies (if applicable) is just as important as anything else. I know our company has a really hard time firing bad employees, and they can get away with crap for awhile.

I personally don't play at work, my desk is in way too high traffic of an area, and I have little self control so I would get nothing done.

Find something productive to do instead of being a shitty employee.

I play at work every time I work from home. Its not hard to sit and kill a mob every 7 minutes or so and work between. I told my team I play games during down time and I don't care if they do as well as long as we meet our goals daily and monthly. Id rather have my team play video games for 10-15 minutes of the hour between tasks than have people on my team that hate having to work. Our team actually has had the highest production rate with the least amount of issues over the last year since I implemented it.

EDIT: Note my team and myself are in IT. I know when they are at home they are playing games/watching Netflix on their other laptop/desktop system. I just give them the approval for it and it makes them function better by not having to sneak around and try not to accidentally say they do it during some meeting/gathering

I am the Information Systems Manager for a company with about 200 users. I have a Helpdesk guy, and a Network Engineer under me. We do very well as I have most of this place automated with System Center.

The firewall content filter we use does not block the Project 1999 website. I use it all the time.

I have also excluded my AD login from all logging on the firewall as we (on a monthly basis) review the firewall logs to see who is doing what on the network. The firewall also logs the sites it has blocked, so it's kind of hilarious to see not only what people are doing, but what they are trying to do.

If I saw a computer with a constant connection to a specific IP address, you bet your ass I'd figure out what that IP address was, then I would rain righteous fire and vengeance upon them.

In short: RL > Pixels. Play at home.

To the people saying "Use Teamviewer! They'll never know!" you fail to understand that most forms of VNC don't alert the user that someone has connected, so something like that would play out like this:

Myself or my staff would see the constant TeamViewer traffic in the firewall logs
I'd have one of my guys "babysit" your desktop via VNC on their 2nd or 3rd monitor
We'd see you logging into your home PC and firing up EQ
We would ruin your day

Your results may vary.

Why work at all? Start working on that diabetes and you'll be on disability and playing EQ 18 hours a day in no time.

https://www.youtube.com/watch?v=u6XAPnuFjJc

EDIT: this isn't the right video I was looking for but it's still a good one. The one I was looking for said that workers who get 10 minutes of goof off time per hour are more productive than those who work the full 60 minutes.