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For your usage it is not worth spending all the money a Vaio will cost you. Even Dell laptops are more expensive than many others. Look at Acer and Asus laptops with a dual core and 4Gb of RAM (memory) and you can save money.
Instead of paying for Microsoft Office just to have Excel, download OpenOffice free of charge - that will handle your spreadsheets and create new ones as well as all the other features MS Office offers.