The program MRT.exe keeps using 50% of my cpu all the time how do I make it stop

First of all, most of the people who respond in this forum are not related to Microsoft.  Unless the responder is identified as a "Support Engineer" or a "Microsoft System Moderator" or the like, he or she is not employed by Microsoft.  Thus, whoever you "connected live to" was not one of our "associates."

MRT.exe is the Microsoft Malicious Software Removal Tool.  A new version of this tool is included with the critical updates every month on "Patch Tuesday" (the first Tuesday of the month).  It should run once -- at the time you download it -- and then be dormant for the rest of the month unless you manually start it up.

Apparently, the unnamed person with whom you dealt didn't fully understand this.

Have you ever received a message to the effect that the MRT found something? 

Click Start > Run then type the following in the Run box and click OK
   
%systemroot%\debug

A Windows Explorer window will open and you should see -- at least -- a file named mrt.log.  You may well see another file named mrt.log.old, which is last months log.

Open mrt.log with Notepad.  You should see something like the following:

---------------------------------------------------------------------------------------

Microsoft Windows Malicious Software Removal Tool v3.19, May 2011
Started On Wed May 11 01:54:01 2011

Results Summary:
----------------
No infection found.
Microsoft Windows Malicious Software Removal Tool Finished On Wed May 11 01:57:25 2011


Return code: 0 (0x0)

If there is an ERROR in the log, post back here and/or see http://support.microsoft.com/kb/891717

MRT.exe should not run continuously.  If it does, something is wrong.

MRT.exe should be located in C:Windows\system32.  If it is not there, search your entire drive, making sure to check the search options to "search system folders, " "search hidden files and folders," and "search subfolders."  If you find MRT.exe somewhere other than C:\Windows\system32, it probably is malware masquerading as the real Malicious Software Removal Tool.

Wherever you find it, delete it.  You can download the current version of MRT here. 

I also suggest that you scan your system with free MalwareBytes Antimalware and <removed> Be sure to update both scanners before running them.

If, after you delete MRT.exe, you get an error message at startup complaining that MRT cannot be found, download and run Autoruns.  Click the "Logon" tab and look in the "Image Path" column for the MRT.exe.  If it isn't shown in the Logon tab, click the "Everything" tab and use the File > Search tool.  An idiosyncrasy of the Autoruns search tool is that you have to move the selection line below the "found" item before you "Find Next."  Once you find the entry with MRT.exe, delete it.