How to find out logged in user remotely in AD

Hey guys, I am starting a search on google now but I wanted quick help on how i can find out users currently logged on. This is in an AD environment with multiple subnets. However here are few constraints:
I cannot use windows event logs or session manager to see who is logged on.
My question is very specific, I need to know if there is any software / utility (preferably utility & free) that I can use to find out which user is logged on in multiple machines – around 5000.

Thanks in advance.

Just curious why you cant use the admin utilities..such as session manager?/

I use a free utility(very old version...works fine)...not sure if it will do the subnets....
GFI Languard Network Scan v2.0... you can change the subnet...so may be able to get the info you need/?/

Not sure if it is even available for download anymore....

EDIT...sorry not showing the username logged in...comes up no one logged in....which I know is false

Must be some service pack or firewall blocking access...I am not running as domain admin ..that may be the issue.

Can you run as a domain admin??

MLF

Look what I found...

http://www.windowsnetworking.com/kba...sloggedon.html

MLF

I have domain admin privileges. What matters is I should know which user is logged in where. It can also be a particular user.

We use an in house application that log's on every machine in the AD. Hence I cannot user the windows logs because even if I keep log size as 128 MB it usually gets filled up in a day or so.

About the nbtstat command.. I knew about it.. But it can't do the entire IP range that’s the only hindrance. I have seen couple of similar utilities based on UNIX but they don't take in IP ranges. I found one that does take in (cant get the link right now) but doesn’t show username. It only shows share information. There is also a utility by Systeminternals but it does not work over the network.
My objective here is to find out how many people are using a particular administrator account at that given point of time.


PS: found the link -http://www.inetcat.org/software/nbtscan.html