Windows XP is obsolete. LOL It works, but it's pretty old.
Get a new Laptop/PC with Windows 7 (preferably 64bit). Get no less than 4GB of RAM.
As for gaming, if you want a laptop that is actually meant to play games with, you probably can't spend less than $1,500 to be honest.
Keep in mind though, a $1,000 desktop computer will play games better than most $1,500 to $2,000 laptops.
The GeForce 105M is not a gaming worthy graphics card for laptops.