Converting from WIndows XP to Windows 7.

You have to do a clean install. There's no "in-place" upgrade from XP to Win 7. So first thing you have to do is back up all your personal files on an external HDD. Then you'll have to wipe the hard drive and install Win 7 and drivers in the correct order, followed by all the Microsoft updates and then your software.

You'll need to have the installation disks and product keys for whatever software you want to install so make sure you have them before you wipe the drive.

You probably don't need to buy Office 2010. I just updated my Dimension 8400 from XP Pro (32-bit) to Win 7 Pro (32-bit) and Office 2003 installed without problems and runs perfectly. If necessary, you can set Win 7 to run Office 2003 in XP compatibility mode, but I really don't think you'll need to do that.

Read this for a good tutorial on installing Windows on Dell PCs.

I have a Dell Dimension 9150, running Windows XP and Office 2003.  I have a lot of software e.g. Adobe CS3 Design Premium.  I wish to change over to Windows 7.   What is the easiset way of doing this?

You can upgrade to 32-bit Vista (without needing a key), and from Vista upgrade to Windows 7. Otherwise, you'll have to reinstall all your software. (Note that Office 2003 is compatible with Windows 7.)

The onboard audio is compatible with Windows 7/8/8.1 and the video may be compatible with Windows 7, too. I clean-installed Windows 7 on a Dimension 5150 (similar to the 9150), and the only hardware missing a driver was the PCI modem.

[quote user="Mark-Surrey-2014"]I have a Dell Dimension 9150, running Windows XP and Office 2003.  I have a lot of software e.g. Adobe CS3 Design Premium.  I wish to change over to Windows 7.   What is the easiset way of doing this?

You can upgrade to 32-bit Vista (without needing a key), and from Vista upgrade to Windows 7. Otherwise, you'll have to reinstall all your software. (Note that Office 2003 is compatible with Windows 7.)

The onboard audio is compatible with Windows 7/8/8.1 and the video may be compatible with Windows 7, too. I clean-installed Windows 7 on a Dimension 5150 (similar to the 9150), and the only hardware missing a driver was the PCI modem.

[/quote]

However in general upgrading via "upgrade" usually yields awful performance and doing so twice will in general yield terrible performance.

The drivers for Windows 7 64 Bit are here (except the modem as the Intel 537E has no Windows 7 driver):

http://dellwindowsreinstallationguide.com/driver-sets/dimension-desktops/dimension-9150-windows-7-64-bit/

Get a new hard drive and clean install so that you can always go back to the old setup.

Vista requires SP1 AND SP2 before it will allow an upgrade install.

Vista home upgrades XP Home

Vista Business Upgrades XP Pro

Vista Business will upgrade either Home or Pro.

If the OP were to go to the trouble of installing a new drive, I'd suggest a 120gb SSD.