Windows 7 not loading on Dell Studio 1535

Hi guys don't know if you can help

Have a Dell Studio 1535 which came with Vista Home Premium installed
It has 4GB Memory (RAM)
Running Kaspersky internet security
Checked Windows 7 Upgrade Advisor and could not find anything that said it was not compatible with Windows 7
So bought a copy of Windows 7 Home Premium
As recommended by Windows 7 I uninstalled these programs

1 - iTunes
2 - ATI Catalyst Install Manager (had to do this by selecting Change & then uninstall in Control Panel/Programs & Features
as no uninstall option with this program for some reason)

Checked system type - 32 bit operating system
So used the 32 bit software

When I tried to install it got error "The upgrade was not successful. Your previous version of windows is being restored. Do not restart your computer during this time"

I know other people have been able to install Windows 7 on this model

Is there anything that you can suggest I try?

I am not majorly 'techie' so if you can help please give basic instructions that a non techie person can follow

Help
Thanks

It is strongly recommended to do a Clean Install rather than an in-place Upgrade which imports any corruption from the prior OS.

Clean Install Windows 7 Boot the Win7 DVD, select Custom install, use Drive tools to format before installing Win7. The DVD will see the prior OS at bootup to allow use of Upgrade version key.

If there was ever a time for a fresh clean install it is with the best OS ever.

If you must for some reason do an in-place Upgrade at this time, try running it with a Clean Boot procedure.