Vista - cmd prompt

I'm wanting to know why I'm when I type "mem" the cnd prompt window it say invadid command.I'm using Vista x64.would appreciate any help on this and if possable the correct command so that I can find out the correct command to use.

i think the memory command was removed in vista, there is a detailed memory diagnostic tool within windows, just type "memory" in the start menu and it will bring up a memory diagnostic tool, but you need to restart to find out the results, if you just want to view your memory allocations then you can do this within windows as well, just type "reliability" in the start menu and it will bring up the reliability and resource monitor up and you can look at everything from memory commit charges to processor strain.

You could also try Process Explorer which can replace Task Manager from here which can also show handles and dll's for a process:

technet.microsoft.com/en-us/sysinternals/bb896653.aspx

Check in C:\Windows\System32 for the file mem.exe.
It's present in my 32 bit VM of Vista Ultimate,
It's not present in my 64 bit Vista Ultimate
I'd have to assume that it wasn't coded into the 64 bit versions for some reason (it's not in my 64 bit Win7 either).