Downgrade from Windows Vista Ultimate to XP Pro SP1, without doing a clean install?

I have recently installed vista ultimate, but do not want it any more. I want to know downgrade to XP Pro, which I have the disc for. I also have a seperate Product Key for XP Pro.

When I insert the XP pro disc, the install XP option is greyed out. I can enable the option by running in a compatibility mode, but nothing happens when i click it.

I do not want to backup my data and do a re-install, as i do not have a drive where i can back it up, and i wish to keep all of my programs and everything else. I know you can upgrade from xp to vista whilst keeping all of your data, is it oppisite to do the reverse whilst keeping everything?

Please help as i just want my old XP back!!!

Downgrade from Windows Vista Ultimate to XP Pro SP1, without doing a clean install?microsoft works

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EDIT:

Did you install all of the drivers?

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You can't downgrade

You have no choice but to do a clean install

Just back up all your data to CDs or something

Sorry, I know that's probably not what you wanted to hear

It'd be a bit of a pain, but I do have an idea:

-Right-click "My Computer" and choose "Manage"

-Go to "Disk Management"

-Inside "Disk Management" right click your C: drive and choose "Shrink"

-Shrink it by about half. Now the space you shrunk will become "unpartitioned" space.

-Right-click the "unpartitioned space" and choose "Create new volume"

-Make the "new volume" use all of the "unpartitioned space" and format it as NTFS

-Now boot from the XP CD, and install it to the "new volume" you just created.

-Once XP is installed, copy all of your files to the "volume" where you installed XP.

-After you have copied all of your files, make a Gparted live CD:

http://download.tuxfamily.org/gpartedliv...

-Boot from the Gparted live Cd and DELETE the old Vista partition.

-Now right-click the XP partition and choose "Resize"

- Now resize the XP partition so it uses the whole hard drive.

-Now just reboot and you will have successfully gotten rid of Vista without losing data.

Downgrade from Windows Vista Ultimate to XP Pro SP1, without doing a clean install?windows mobile internet explorer

Format the hard drive and reinstall Windows with your disk.
why do u want to downdrade back 2 XP? i have 2 vista prenium laptops that i was planning to downgrade but vista runns better than XP. Thats cuz i'm running Vista's SP1.

well try calling a pc shop and ask how you can do that
I don't know about all this,I hate vista too,so I will be watching the answers you get.I get nothing but problems with this Vista.
I would have to agree with you, I wouldn't want Vista either. You may want to turn off your computer and boot from the disc instead of just installing it. You do need to do a clean install, obviously an upgrade is not going to work. Try it, keep me posted. Oh, and alot of files that you had on your computer for drivers and stuff will be gone if you do this, so I would get all the drivers for all the internal components and internet service first before doing this. Good luck.
You cant downgrade, you must do a fresh install.
What? Do you really think Microsoft would make it easy for you?

Try booting with the XP disk in the computer and make sure that your boot order has the cdrom first.

If that doesn't work, go into your MBR (master boot record) and change the parameters back to xp. Careful on this one because if you mess this up, it can make your disk inoperable unless you have Linux to rescue it.
You could look into dual booting it-

http://apcmag.com/5485/dualbooting_vista...

You could also partition your disks, dump your data onto your second partion and reload XP or if you have a second harddrive, you could put it in as a slave, dump your data onto it and then reload your original HD with XP.
Sorry, you don't really have any options. Downgrading isn't supported. You have to format your drive and rewrite the boot record to install XP.
It can't be done.