Posts order on different pages

1. How can I change the ordering of posts on a particular category page ? I want the older ones first, in an ascending order. I only want this to reflect to a specific category page. Can it be done ?

2. Again I want to change the ordering of pages on another category page, but this time I want to be something like this: 4,7,5,3,8,11,43,26 (where numbers are posts id’s)

I’m using the latest WP version, 2.6.2.

I would be grateful for any solutions. Thanks!