vista xp and software

Hi I had a couple of questions so I figured someone might be able to help me her

1. I was wondering if someone knows if any software for windows that is a caller id program I want there number to pop up on my screen when someone calls

2 I thought vista was a memory and cpu hog I just installed it on a 2.43 GHz single processer with 512 mb memory and its okay so why is that also I hate to do this but what are the disadavanteges of upgrading to vista ultimate


thanks in advance