From Bioware's site:
General CD Install Troubleshooting
If you are having problems getting BG2 to install or BG2 asking for a CD5, you may want to try some of the following suggestions.
When changing CDs during the installation, let the drive spin-up and then stop. Then click OK and see if the installer recognizes the disc change. Do this for all the CDs that are requested.
Try checking for a firmware/BIOS update for your CD or DVD drive. We have had several reports of sucessfull installs of BG2 once a firmware update was applied. You will have to check with your CD/DVD drive manufacturer for this kind of update.
If for whatever reason you are unable to do a Recommended or Full install, but you can do a Minimum install, please read How to "fake" a larger install from a Minimum.
If you have multiple CD/DVD drives, only install from one and do not try to use all of your drives. For some reason, this is confusing InstallShield.
If you cannot do any install without getting some sort of error or crash and you have about 5 Gig of free hard drive space, you can try to copy all 4 CDs to your hard drive, then run the install from there. Please note, you must copy all 4 CDs to the same directory for the install to run. If you get prompted for the next CD, then you have not copied the files over properly, or you have missed some.
Try turning off DMA for your CD/DVD drive. For some people, this has allowed them to install. You can find this checkbox by going to your Control Panel, then to System, then to the Device Manager tab. Find your CD/DVD drive and bring up its Properties, then go to the Settings tab.
Try turning off your CD/DVD read-ahead. For some people, this has allowed them to install. You can find this slider by going to your Control Panel, then to System, then to the Performance tab. Down in the Advanced Settings frame, press the File System... button and move the slider all the way to the left. You may need to restart for this setting to take effect.
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The RudeDawg
Known in these Forgotten Realms as Perin LightEyes
and my girlfriends, Pamila and Phil