firstly... you're honestly wasting your time with a static IP and remember if people spoof your IP (and on the iBurst network it happens alot) and it gets entered into a blacklist database or spam database.. you're pretty much screwed if you plan to connect to computers on the net..
I'm not sure you mean by 'what' is using it, you can try reverse DNS the IP with 'nslookup xxx.xxx.xxx.xxx' in a command prompt to find the hostname but its probably going to look like a normal iBurst user hostname and you can try pasting the ip in your browser to see if they run an httpd and if so what they have on there or port scan will let you know alot about them... but thats not the sort of activity people appreciate