Windows 7 Upgrade Advisor

What Model PC?   Could be the PC isn't compatible and won't even run the upgrade advisor???   Do not have other programs running such as Internet Expolorer, e-mail, etc when you run it.  Some Antivirus programs could also be interferring.

Thanks for the reply. Turned everything off (all running programmes, anti virus, firewall etc) and still will not run. Model is Dimension E520.

I can't say why the upgrade advisor won't run, this is the first case I've seen.  Have you tried downloading the advisor again just in case you got a bad download.

Dell supports Vista 32 bit and 64 bit on this model.  The Vista drivers HERE usually work OK for Windows 7, since Windows 7 is basically "Vista improved".   The maximum memory that can be installed in the E520 is 4GB (like my E510) so there is no need to install the 64 bit version, the 32 bit version is all you will need. 

You will have to do a "clean" install, you can't "upgrade" Windows XP to Win 7.  You may want to consider installing a new hard drive and installing Windows 7 on the new hard drive.  That will do two things (1) Maintain the Dell recovery and diagnostic partitions on the original hard drive and also preserve XP if you have to fall back and also it preserves all your user data that you can copy over from the old hard drive.  If you use the existing hard drive it will require backing up your user data (e.g. music , pictures, word processor files, e-mail address book, Internet Favorites, etc)  to some other drive or CD/DVD's as the data will be lost when you reformat.  The Dell recovery partiton will also be corrupted and you won't be able to use that if you wanted to reinstall XP using the Dell recovery partition.  

Most of your old XP software will run in Win 7, there can be problems with some very old software, especially older games. Those that won't run in the native Windows 7 mode will have to be run in a Windows XP "compatiblity" mode (but that will not run ALL old software).