Not possible. There is no upgrade path for XP with 7. You will have to do a clean install. You CAN buy the reduced price upgrade version of 7, but you'll have to do a clean install. You'll want to visit Microsoft's website to figure out which of the like 7 versions of Win 7 you want. Most people are perfectly content with Home Premium, but some want the XP Mode only offered in Pro and Ultimate. There's a feature matrix you can use to figure out which one you want.
And prices will be pretty much the same everywhere, so pick whichever retailer you want. OEMs such as Lenovo only sell Windows with new systems, and occasionally they will offer free upgrades when a new version of Windows is due out within 6 months, but that's merely a concession to keep sales going during those 6 months.
I have an IBM(Lenovo)Type 2530 S/N LR 01033 0511 laptop with Windows XP Professional and I want to upgrade to Windows 7. Possible? If so, where is the cheapest place to download or can I get it through IBM at a reduced price? Thank you for your excellent service and advice.