The forms encoding type needs to be set to multipart/form-data, the action should be left blank and there should only be one form tag instead of 6:
<div id="mainContent">
<div id="leftDiv"></div>
<div id="uploadDiv">
<form action="" method="post" enctype="multipart/form-data" name="form1" id="form1">
<input name="Browse" type="file" size="50" maxlength="200" />
<input name="Browse" type="file" size="50" maxlength="200" />
<input name="Browse" type="file" size="50" maxlength="200" />
<input name="Browse" type="file" size="50" maxlength="200" />
<input name="Browse" type="file" size="50" maxlength="200" />
<input name="Submit" type="submit" id="submit" value="Submit" /></form>
</div>
</div>