initialize the variable just before the do statement:
<?php i = 1; ?>
<?php do{ ?>
reference the $i variable in the ID's:
<div id="p7HGMpn_1_<?php echo $i; ?>" class="p7HGM_panel">
<div id="p7HGMpc_1_<?php echo $i; ?>" class="p7HGM_panel_content">
increment the variable just before the while statement using ++
<?php $i++ ?>
<?php } while ($row_Recordset1 = mysql_fetch_assoc($Recordset1)); ?>