Friendly URL not work! Help Me

[Huynh Nguyen Thoai]

changed htaccess.txt to .htaccess with content: # URL rewriting module activation

RewriteEngine on
URL rewriting rules
RewriteRule ^([0-9]+)\-([a-zA-Z0-9-]*)\.html(.*)$ product.php?

id_product=$1$3 [L,E]
RewriteRule ^([0-9]+)\-([a-zA-Z0-9-]*)(.*)$ category.php?

id_category=$1$3 [L,E]
RewriteRule ^([0-9]+)__([a-zA-Z0-9-]*)(.*)$ supplier.php?

id_supplier=$1$3 [L,E]
RewriteRule ^([0-9]+)_([a-zA-Z0-9-]*)(.*)$ manufacturer.php?

id_manufacturer=$1$3 [L,E]

Catch 404 errors
ErrorDocument 404 /404.php

and ticked Use Friendly URL in Backend but it not work. Help me

[Peter Wilson]

Hello,

bq. For some hosting services such as Dreamhost, by default the option to “open external URLs” is off or disallowed.

http://www.prestashop.com/wiki/External_or_Friendly_URLs/

[Daniel]

I have the same problem and have tried the wiki steps, but it still doesn't work. Any more ideas?
I'm with 1and1 and have put everything in my php.ini and .htaccess files