remove public folder

After some errors I have to remove exchange 2007 and install it again. The
exchange 2007 server coexists with a Exchange 2003 server. When I try to
uninstall I get the error:

â?? The public folder database "Ex2007\Second Storage Group\Public Folder
Database" contains folder replicas. Before deleting the public folder
database, remove the folders or move the replicas to another public folder
databaseâ??

I try to remove it like MS say but no. In Powershell I get this:

[PS] C:\>Get-PublicFolder

Name Parent
Path
----
-----------
IPM_SUBTREE


[PS] C:\>Get-PublicFolder -Server ex2007 "Ipm_Subtree" -Recurse
-ResultSize:Unlimited | Remove-PublicFolder -Server ex2007 -Recurse -Error
Action:SilentlyContinue -Confirm:$False

Get-PublicFolder : There is no existing PublicFolder that matches the
following Identity: 'Ipm_Subtree'. Please make sure that you specifie
d the correct PublicFolder Identity and that you have the necessary
permissions to view PublicFolder.
At line:1 char:17
+ Get-PublicFolder <<<< -Server ex2007 "Ipm_Subtree" -Recurse
-ResultSize:Unlimited | Remove-PublicFolder -Server nsmail1 -Recurse -Error
Action:SilentlyContinue -Confirm:$False

Do any one have something about this issue?