Not enough memory issue (after formating XP from Vista)

My inspiron 1520 came with vista, didnt like it so i reformatted with XP. Got all the proper drivers and everything was working nicely except when I went to restart or shutdown it would take like 15mins. It would close any programs down then go to the screen where it just shows the wallpaper on the full screen and it would stay there for 15mins until it restarted or shut down. But now I am experiencing a new serious problem, I keep getting not enough memory message and this closes my games, movies, webbrowser down.

I have 2gb of ram so what could be the problem?

 

Likely, something you're running has a memory leak. One problem XP had was explorer among other services and process, would eat memory non-stop, even after being closed.

Vista seems less prone to the issue.

But software you have installed, and run can still have the problem. Firefox 2 has had a record for being a memory hog.

 

I have been using XP for a long time on my old notebook and my old desktop, never had those issues. What are my options, if there really arent any quick fix solutions I am thinking something must of went wrong during the format. I don't have many things installed now so I will probably reformat (This time on AHCI instead of ATA, just got a XP CD with the SATA files) and see what happens.