Hello Freakie, and welcome to Seven Forums. Thank you.
In the 64-bit Windows 7 and Vista, Microsoft offers a set of 32 bit executables in the SysWOW64 (Windows on Windows) directory of the system for backwards compatibility.
Since you have the 64-bit Windows 7, there would really be no need for yourself to use anything other than the 64 bit executable of taskmgr.
Hope this helps,