The other thing you may want to think about is Windows Vista, and the new version of Windows coming out in October.
Vista has had some very bad press, and for that reason Microsoft are replacing it quicker than they normally would with Windows 7 in late October.
So they dont kill the sales of PCs and laptops over the next few months they have said that they will offer a free upgrade to Windows 7 if you buy certain Vista computers now.
Dell have already announced this offer on some of their laptops, so it may be worth looking at them.
They are offering the Inspiron 15 with a free upgrade to Windows 7.
More here
http://tinyurl.com/l2q4an