First things first check the CD/DVD for scratches or marks and clean them.
Try renaming the InstallShield folder.
Double-click on the My Computer icon.
Double-Click on the C:
Double-Click on Program Files then on Common Files.
Right-Click on the InstallShield folder.
Select Rename.
Rename it to InstallShieldOld.
Start the installation again to reinstall the InstallShield components with the newest version.
Try installing the game in Windows safe mode.
Also try disabling all unnecessary background tasks including your anti-virus.
If that doesn't work try a copying the files to your hard drive and installing from there.
FOR CD:
Go into My Computer.
Open drive C.
Right-click inside the window and select New, and then Folder.
Name the folder as Disk Images (it is important that the name has a space in it).
Open the disk images folder.
Right-click inside the window and select New, and then Folder.
Name this folder Disk1.
Repeat steps 6 and 7 while substituting Disk1 for Disk2 and so on until there are 4 'Disk' folders followed by a number 1 through 4. it is important to note there must not be a space between "Disk" and the number.
Insert Disk 1 of The Sims 2 into your CD-Rom drive and if the autoplay starts, cancel it.
Go into My Computer.
Right-click on your CD-ROM drive and choose Open.
When you see the contents of the disk in the Window, click on Edit at the top of the window and choose Select All.
All the contents of the disk should now be highlighted, click on Edit at the top of the window again and choose Copy.
Open the Disk1 folder you created under C:\Disk Images; click on Edit at the top of the window and choose Paste. This will copy the contents of the CD into the Disk1 folder.
Repeat steps 9 through 14 for the remaining disks until you have copied each disk into its appropriate folder.
Once all the disks have been copied, remove ALL CD's from any drives.
Open the Disk1 folder under Disk Images and double-click on autorun.exe to start the installation.
To save disk space, you can delete the Disk Images folders after the installation is complete.
FOR DVD:
Insert the DVD into the DVD-rom drive. Exit the startup menu when it comes up.
Double click My Computer, then right click on the DVD-rom drive with the game DVD in it and select Explore.
Hold the CTRL key and then hit A. That should select all the folders and files.
Then hold CTRL and hit C. This will not look like it does much, but it's preparing to copy the files.
Close that folder and go to your desktop. Right click anywhere BUT on an icon, and Select New, then Folder. Name the folder Sims2 DVD.
Then double-click that folder, and hit CTRL and V. This will begin copying the files from the DVD.
Once the files are copied, remove the disc from the drive.
Double-click on the Setup icon in the folder.
You may delete the Sims2 DVD folder once the installation is complete.