Ah, another "fan" of Vista, I see.
Okay, if you REALLY want Vista off your computer and want to retrograde back to XP Pro or something else, here's a few tips:
MAKE SYSTEM RECOVERY DISKS BEFORE YOU DO ANYTHING ELSE.
1. Make sure you have the OS disks for whatever system you want to replace Vista with. A brand new, still-sealed-in-plastic, authentic-license disk is best.
2. Make sure you identify ALL of the hardware on your computer (the motherboard, drives, display, display adapter (video card), disk drives, USB controllers) and then search the net and download all the drivers for your hardware. Save them to a separate disk (CD, floppy, or USB) and have them ready when you reinstall the OS. XP might not easily identify your hardware. Make sure the hardware drivers are appropriate to the OS you are going to install.
3. Make sure that your system will accept an OS retrograde. Some newer systems, especially those coming from Acer, won't accept any OS other than Vista. It's a good idea to make sure you download the correct BIOS for your motherboard as well.
4. Vista is known for being an "anchored" system, meaning it won't let you downgrade to another OS. To get past this, you might need to completely wipe your hard drive and start from scratch with the OS disk.
WIPING THE HARD DRIVE
1. Make sure ALL of the data that you value is backed-up on another drive or to disk. If you are using an alternate drive, make sure you disconnect it from your computer before proceeding.
2. Download DARIK'S BOOT AND NUKE and save it to a CD or USB drive (Carefully select the correct version for your needs).
3. DISCONNECT your computer from the internet and/or any network cables that are attacked. Disconnect any peripherals (such as a printer, scanner, router, or hub).
4. Darik's Boot And Nuke will COMPLETELY wipe ANY hard disk it finds. Run the program and select your computer's drive that contains the Vista OS. It will take a while because it is erasing EVERYTHING.
5. Once it is done, insert your new OS disk for your system retrograde and reboot the computer. Follow the instructions, and have your hardware drivers disk handy.