Hello :)
In PowerShell make sure that this returns the files you want to remove:
$x = 30 # x days :)
Get-ChildItem "C:\YourFolder" | Where-Object { $_.LastWriteTime -lt (Get-Date).AddDays(-$x) }
If it does, add this onto the end:
Get-ChildItem "C:\YourFolder" | Where-Object { $_.LastWriteTime -lt (Get-Date).AddDays(-$x) } | Remove-Item
If you want to test it with Remove-Item on as well you'd need this:
Get-ChildItem "C:\YourFolder" | Where-Object { $_.LastWriteTime -lt (Get-Date).AddDays(-$x) } | Remove-Item -WhatIf
Remember that files deleted like this won't be going to the recycle bin, so make sure it really only gets what you want first.
HTH
Chris
PS. PowerShell is here if you don't already have it installed:
http://support.microsoft.com/kb/968929