I have installed Ubuntu 11.10 on my Acer netbook as a dual boot with the default Windows XP on said netbook. Now I need only Windows XP and want to completely uninstall Ubuntu 11.10, there is no cd drive in my netbook. Any help would be greatly appreciated.
Follow the instructions regarding easybcd as described
After you reinstalled the windows bootloader you can delete the ubuntu partion using a live cd/usb and running gparted.
If you have a Wubi install then you can just remove it from the Windows 'Add/Remove programs' tools (or whatever it's called these days).
If you installed it some other way (USB?) as a full dual-boot system, then you can probably restore it using a USB CD drive - but I'm sure you already thought of that. (Maybe you could put a Windows CD image on a USB drive, but I don't know?)
If none of that works then you could try using a virtual machine. If your machine can't handle real VMs (and many netbooks won't be able to), then
kvm can simulate a machine the hard way, slowly, as long as you have enough memory.
kvm will boot from an iso image of a Windows CD (or maybe a network mounted CD drive, slowly), and you can set your virtual hard drive to be your real hard drive
/dev/sda (or whatever it's called on your system - you'll need to be
root to access it), and then you can let it do a repair. IF THIS GOES WRONG BAD THINGS WILL HAPPEN, so wait until somebody has found the obvious flaw in my plan and posted it in the comments.
Don't ever try to do a full install this way though: a) bad things happen if you wipe the drive your OS is running from, and b) Windows detects hardware at install time, not run time, and the virtual hardware won't match your real hardware, so the result won't boot. (Although, I have actually used this technique to install Linux on a drive that I had physically removed from another machine that had no CD or boot-from-USB feature.)
Once the Windows boot loader is restored, you can reboot into Windows, and use normal Windows tools to rearrange/reformat/delete/extend the drive partitions to your taste.