What's the configuration for your pc?
technically they both can be run at the same time if you use virtual machine environment.
it's a bit complicated , and i wouldn't recommend it to a newbie.
Do not play with your OS registry, but if you are desperate, always create a backup BEFORE you edit it.
if you are on win 7 and use (win xp mode),you would need a compatible processor for it, google it!, you can seamlessly use both odin's at the same time without any problems, and it's just as easy as minimizing one and using another.
I would warn you though that the above process HAS NOT BEEN TRIED by me and therefore you are pretty much on your own if you wish to try, btw below are other solutions that might work :-
the problem lies in the registry, installing odin for one broker, does not make a unique entry for that broker in the registry, it creates a single entry at "HKEY_LOCAL_MACHINE\SOFTWARE\ODIN", now if another similar registry entry could me made to co-exist there wouldn't have been any problems, but windows does not allow such a feature yet! i.e until win 7,(may be in the future they would, i mean they have done a damn good job with "WinSXS" "windows side by side feature")
so the only way around this problem is to create an entirely different registry, either only for the application or a completely new registry, if you are in the know, you may use
1. "sandboxie" to emulate virtual registry for odin, or
2. "VMware ThinApp"(not a freeware.) to create a portable version, you would have to do it everytime the broker upgrades, patches the reg entries for odin or upgrades the "master files"(the files which hold the information about the exchange scrips). (Not a good idea)
3. "VMware Player" (freeware) (you will still need win xp image, google how to make a image with your win xp disc for vmware player) to create a virtual machine for xp , install one of the odin's in it. (highly recommended, only if you know what you are doing).
Note:- All the above mentioned methods Have NOT been tried by me but they should work especially the one's about the virtual machine.