أريد تركيب اوبونتو مع الحفاظ على ويندوز فيزتا الموجود مسبقا

Wa aleikom al Salam

Use this guide to dual boot ubuntu and Vista with vista being pre-installed on the PC http://apcmag.com/5046/how_to_dual_boot_vista_with_linux_vista_installed_first

If you already have a partition for ubuntu, you can skip the first few steps and just install ubuntu using the manual option and edit the partition on D.(Delete it, create new partition with ext3 filesystem, make sure you leave some free space so again you can create the swap partition with it, all in the partition editing step during ubuntu installation.)

Finally, make sure you backup your files, overall repartitioning is a safe procedure, however, the success of the operation is not guaranteed. If any problem occurs you can restore vista from the CDs provided with your PC and restore your data from the backup you made. Sorry for not replying in Arabic but my OS doesn't have Arabic input support enabled.