Rewriting Dynamic URLs will Affect SERP

[Abdelrhman Fahmy]

my current site ranked well for the static pages while the Dynamic pages (which are more than 400) doesn't show in the first 100 SERP (it's a shopping cart with long path to the dynamic pages like site.com/dir1/dir2/product.asp=id1=#*$!&id2=yyy) and i want to use ISAPI_rewrite to rewrite that long urls to static and short URLS)

and my question is :
does that change will affect my current site ranking and SE position as the search engine may recognize the new static pages as duplicate.

[Prolific]

i recently did just that. write some code to handle the old pages and redirect via 301. this did wonders for our product pages in the serps. our product pages actually display PR now.

[Abdelrhman Fahmy]

I've read in a previous post that i may disallow indexing of the Dynamic ASP pages to prevent the duplicates