You have several options here:

1. Use the SMS 2.0 client cleaner available from here.

2. Use the information provided from the following link: How Can I Uninstall the Client Using a Batch File?

3. Delete all of the boundaries from your Site Servers. Once the boundaries are removed, you should then see (assuming that the Logon Installation method is on), the corresponding SITES sub-folder in the PDC's SMSLOGON\SITES folder disappear; it should then replicate to all BDC's (the fact that the folder has gone), and once the folder is gone, the clients (upon the next logon or 23 hour CCM cycle) will see they don't belong to any sites and de-install themselves.

4. Use 'IFMEMBER.EXE' to see if the user is part of a group called "Remove SMS" and if the statement returns true, go to  the section of the master login script which contains 20clicln batch code and accesses the rest of the files which are replicated to all logon servers:
   
   IF "%COMPUTERNAME%" == "BROKENSMS" GOTO SMSBUHBYE
   :SMSBUHBYE
   20cliclean code
   
   Using this process the cmd window will appear to hang for some time - this is unavoidable. You will also need to hardcode a list of computernames in the script to get this to work.

5. Using  20clicln.exe:
   
   i) Install SMS Support tools on your PC
   
   ii) There is a batch file associated with this 20clicln.exe i.e. 20clicln.bat, this actually calls this exe along with few other scripts. You need to have the following files kept on a shared folder some where on the network. Give everyone read/full control. Refer to Tools.htm to more information.
   
   iii) Enable auto admin logon by setting the following registry keys on required computers. ( In our case, we do have scripts to achieve all these )
   
   [Version]
   Signature = "$Windows NT$"
   
   [DefaultInstall]
   AddReg = AddReg
   
   [AddReg]
   HKLM,"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon","DefaultUserName",,"administrator"
   HKLM,"SOFTWARE\Microsoft\Windows
   NT\CurrentVersion\Winlogon","DefaultPassword",,""
   HKLM,"SOFTWARE\Microsoft\Windows
   NT\CurrentVersion\Winlogon","AutoAdminLogon",,"1"
   
   
   iv) Write a batch/cmd file ( ex: deins.cmd) to mount the shared folder where the 20clicln.exe and dependent files have been kept and call the batch file 20clicln.bat with in this batch file.
   
   v) Now set RUNBATCH key to call this batch script:
   
   [Version]
   Signature = "$Windows NT$"
   
   [DefaultInstall]
   AddReg = AddReg
   
   [AddReg]
   HKLM,"SOFTWARE\Microsoft\Windows\CurrentVersion\Run","RUNBATCH",,"deins.cmd"
   HKLM,"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon","DefaultUserName",,"administrator"
   HKLM,"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon","DefaultPassword",,""
   HKLM,"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon","AutoAdminLogon",,"1"
   
   Now, if you reboot the systems, each NT system would login as Administrator of that machine and de-installs the software.
   
   You can apply these *.INF files, the sequence can be controlled by using rundll32.exe, for example:
   
   c:\winnt\system32\rundll32 setupapi,InstallHinfSection DefaultInstall 128 c:\test\autoadmin.inf
   
   Refer unattended installation in any of the TechNet articles for more details.