i don't know asp well enough to type it off the top of my head, .. but here is some suedo code.
mySubmittedValue will have to be set somewhere above the for loop.
Code:
<select name="Products" id="products" onChange="DescTest()">
<%dim j
for j=lbound(arrproducts) to ubound(arrproducts)-1
Response.Write "<option value=" & arrproducts(j,1)
If arrproducts(j,0)= mySubmittedVariable
Response.Write " selected"
End If
Response.Write ">" & arrproducts(j,0) & "</option>"
next
%>
</select>
like i said, i don't know asp very well, but this is the logic i might use with PHP. ( with a lot less code

)