>Should I have a cooling mat for my 17 inch Alienware laptop or is it ok if I have it on top of a cardboard box or blanket?
Blanket? No, it will cause it to overheat. Cardboard box? It should be okay, as long as there is space for the fans to catch air.
>What's a good mouse also that I should get?
If you are going to be playing games, I would suggest a wired mouse so that there is no lag. If you are just going to be browsing, a wireless mouse is fine. But I suppose the biggest factor is your budget. How much money are you willing to spend on a mouse?
Check out this website for a comparison of mice:
http://www.logicalincrements.com/peripherals/#mouse
>http://accessories.us.dell.com/sna/products/PC_Accessories/productdetail.aspx?c=ca&l=en&s=dhs&cs=cadhs1&sku=A7116999
I have that mouse but I never used it. I have heard it is good though.