To upgrade from win XP to win 7 what is the charge please? Thank you.
I'd say roughly between 95 and 185 USD. Roughly.
Look on your favorite online retailer's web page or visit your favorite physical retailer.
Please have chosen what edition of Windows 7 you want to upgrade to. There is not just one... http://windows.microsoft.com/en-US/windows7/products/compare
You'll need 32-bit since you are upgrading from Windows XP. Although since you will be upgrading from WIndows XP - which is a completely clean installation anyway - you can switch to 64-bit *if* your computer is capable.
Also, highly suggested you make sure all your hardware and software is compatible with Windows 7 (motherboard chipset, audio device inside the computer, video device inside the computer, network device(s) inside the computer, printers/scanners/cameras connected to the computer, etc. for hardware; office suites, image editing, email applications, other third-party applications, etc. for software...) by checking with the manufacturers of each component/product. If it is not compatible and you need it - probably better not to upgrade.
What are your system specifications - in particular look at these items: Processor/CPU (speed and number of cores), Memory/RAM (total amount), hard drive space (total and free) and video card (make, model and amount of dedicated memory)?
Go ahead and run the Windows 7 Upgrade Advisor. It is not the end-all/be-all of the situation and does not substitute for the collection of information above. It is just wise to do.
http://windows.microsoft.com/en-US/windows/downloads/upgrade-advisor