Two possibilities.
First - Your current system hard drive is partitioned. then you can format that partition and install another operating system.
If it is not partition, then - purchase a small hard drive and install your second operating system on to that drive.
THE MOST WORK - Back up your data to a DVD/CD, put your original Operating System disk into the computer and reinstall. Select NEW INSTALL (READ THE SCREEN)
Delete all partitions, create three partitions, two should be 20GB each.
Complete installation, install motherboard utilities and drivers, anti virus and firewall.
Install secon Operating System into the 2nd 20GB partition, Install motherboard drivers and utilities from the motherboard CD.
Go to www.microsoft.com - UPDATE and let this site update your computer. You have to boot into each software before going to Microsoft.
Computer Help Page
http://www.nu2.nu/pebuilder/ http://oss.netfarm.it/winpe/
http://www.paraglidernc.com/ http://www.bootcd.us/
VISTA Upgrade or Requirements
http://www.microsoft.com/windows/products/windowsvista/buyorupgrade/upgradeadvisor.mspx
http://www.diskgenius.com/
http://www.pcbeginner.com/tools/pcdoctor.htm
http://www.pcguide.com/byop/index.htm
http://www.ntfs.com/boot-disk.htm
http://www.softpedia.com/get/System/Boot-Manager-Disk/
http://www.freedownloadscenter.com/Best/ntfs-boot-iso.html
http://www.disk-image.net/products.htm
http://www.bootdisk.com/bootdisk.htm
http://www.errornuker.com/info/01.php?hop=product1
http://www.nu2.nu/pebuilder
http://www.majorgeeks.com/downloads2.html
http://www.ntcompatible.com/Acronis_True_Image_9.0_Build_2337_s61449.html
http://www.theosfiles.com/
http://www.data-recovery-reviews.com/windows-startup-disasterrecovery.htm?gclid=CMSl0b7X2YcCFSJxYAodKy6Lpw
http://www.winternals.com/
http://www.pcworld.com/downloads/file/fid,25181-order,1-page,1-c,alldownloads/description.html
http://www.softpedia.com/get/System/Boot-Manager-Disk/Windows-XP-PowerPacker.shtml
http://www.extremetech.com/article2/0,1697,674406,00.asp
http://windows.about.com/od/tipsarchive/l/bltip632.htm
Visit our Helpdesk for PC Bug Doctor
http://www.maximumsoftwaresupport.com
PC Beginner software
http://www.pchell.com/support/limitedconnectivity.shtml
http://www.nu2.nu/pebuilder/
http://www.bootdisk.com/utility.htm
Chapter 1: Purchasing Components
Chapter 2: Component Overview
Chapter 3: Installing the CPU, Heatsink, and RAM On The Mainboard
Chapter 4: Installing The Mainboard In The Case
Chapter 5: Installing Drives
Chapter 6: Connecting Components
Chapter 7: Installing AGP and PCI Cards
Chapter 8: Testing the System and Completing Assembly
Chapter 9: Installing Windows XP
Chapter 10: Configuring Windows XP
Chapter 11: Installing A Dual Boot Operating System (Linux And Windows XP)
Chapter 12: Home Video -- “So, You Want to Be the Next Steven Spielberg?”
Chapter 13: What’s Next?
http://www.hardwareanalysis.com
http://www.majorgeeks.com/download4007.html
http://www.nu2.nu/bootdisk/
http://www.free-pc-checkup.com/
http://www.pctools.com/registry-mechanic/?ref=Googlebspeed
http://pcperformancetools.com/recovermyfiles.htm
http://free.grisoft.com/freeweb.php/doc/...
http://www.download.com/3000-2144-100459...
http://www.worldstart.com/tips/tips.php/...
http://www.aarp.org/learntech/computers/...
http://www.microsoft.com/windowsxp/using...
http://www.zonelabs.com/store/content/co...
BUILD YOU OWN COMPUTER:
www.directron.com
www.newegg.com
A Good PC Cleaner
http://www.pc-error-cleaner.com/?gclid=COzW8YTD0ogCFRL1YgodAD0pbg
NTFS Boot Disk:
http://www.ntfs.com/boot_disk_includes.htm
To place Active@ KillDisk Pro onto a floppy disk type the following at the command prompt:
COPY G:\KILLDISK.EXE A:
COPY G:\DOS4GW.EXE A:
The above assumes that the G:\ drive is the bootable CD-ROM drive and the A:\ drive is the floppy disk drive.
DOS4GW.EXE is a required file for Active@ KillDisk, Active@ UNERASER and Active@ Disk Image.
http://www.download.com/BartPE-Bootable-Live-Windows-CD-DVD/3000-2094_4-10611130.html