In short, no.
Not possible to go from XP to 7. It is possible to upgrade from Vista to 7, or from XP to Vista, but not XP to 7.
Only way to upgrade to 7, the newer operating system, is to have a 64-bit capable processor and do a clean install.
If the desktop only has a 32-bit capable processor, it is not possible to install a 64-bit operating system with it. If your desktop only supports 32-bit, then 64-bit will not work or even install. One way to fix that is to install a new 64-bit capable motherboard along with a new 64-bit processor, memory, etc,.
Is the Dell 64-bit?
Only way you will know how much this will cost is by calling Microsoft.
I have a Dell desktop I am currently running with Windows XP SP3,I would like to upgrade it to Windows 7 Home Premium 64 bit and have a couple questions.1.I used MS windows upgrade advisor and most of my hardware will have drivers I can download.I recently updated a laptop that was running win Vista 64 bit with a clean install of windows 7 Home Premium 64 bit vs. I wanted to know if I can use that same CD to clean install on my desktop and obtain another windows license from MS?. If so how much does it cost to obtain another license?Thank you very much in advance.