static void Main(string[] args)
{
string downann = @"downloads\";
string homepath = Environment.GetFolderPath(Environment.SpecialFolder.UserProfile);
string downloadsdir = string.Format(@"{0}\{1}", homepath, downann);

DirectoryInfo downloadsinf = new DirectoryInfo(downloadsdir);

foreach (System.IO.DirectoryInfo gi in downloadsinf.GetDirectories())
if isFolderSolid(gi , ".jpg") {
 // move it to pictures
}
if isFolderSolid(gi , ".avi") {
 // move it to movies
}

}

private void isFolderSolid(System.IO.DirectoryInfo gi, String type) {
foreach (FileInfo fi in gi.GetFiles())
{

//TODO add a check to make sure gi has at least one file

name = fi.FullName()
if (name.SubString(name.Length-3,3) != type)
	return false;
}