This has been taken from the Bioware site, it's got all sorts of stuff to help with problems your having with the game.
http://www.bioware.com These are the instructions on how to change a minimal installation into a recommended or full install of the game.
How to "fake" a larger install from a Minimum install
Minimum to Recommended Install
1. Do a Minimum install.
2. Edit your "baldur.ini" file. Change the line "Install Type=1" to "Install Type=2"
3. Copy the following files from CD2 to your BG2 directory, where [cddrive] is the letter of your CD-ROM drive and [BG2] is the location of your BG2 install
[cddrive]\CD2\Data\CREAnim.bif ===> [BG2]\data\CREAnim.bif
[cddrive]\CD2\Data\CREAnim1.bif ===> [BG2]\data\CREAnim1.bif
[cddrive]\CD2\Data\GUIMosc.bif ===> [BG2]\data\GUIMosc.bif
[cddrive]\CD2\Data\MovHD0.bif ===> [BG2]\data\MovHD0.bif
[cddrive]\CD2\Data\NPCSoCD3.bif ===> [BG2]\data\NPCSoCD3.bif
[cddrive]\CD2\Data\NPCSound.bif ===> [BG2]\data\NPCSound.bif
4. Copy the following files from CD3 to your BG2 directory
[cddrive]\CD3\Data\CD3CreA2.bif ===> [BG2]\data\CD3CreA2.bif
[cddrive]\CD3\Data\CD3CreAn.bif ===> [BG2]\data\CD3CreAn.bif
[cddrive]\CD3\Data\CDCreAni.bif ===> [BG2]\data\CDCreAni.bif
5. Copy the following files from CD4 to your BG2 directory
[cddrive]\CD4\Data\CD4CreA2.bif ===> [BG2]\data\CD4CreA2.bif
[cddrive]\CD4\Data\CD4CreA3.bif ===> [BG2]\data\CD4CreA3.bif
[cddrive]\CD4\Data\CD4CreAn.bif ===> [BG2]\data\CD4CreAn.bif
You now have a Recommended install.
Minimum to Full Install
1. Do a Minimum install.
2. Edit your "baldur.ini" file. Change the line "Install Type=1" to "Install Type=3". Also, you will need to edit the [Alias] section. Make the following changes where [BG2] is the location of your BG2 install
[Alias]
HD0=[BG2]
CD1=[BG2]\CD1
CD2=[BG2]\CD2
CD3=[BG2]\CD3
CD4=[BG2]\CD4
3. Copy the following directories (and all their contents) from the BG2 CDs to your BG2 install folder, where [cddrive] is the letter of your CD-ROM drive and [BG2] is the location of your BG2 install
CD2
[cddrive]\CD2 ===> [BG2]\CD2
CD3
[cddrive]\CD3 ===> [BG2]\CD3
CD4
[cddrive]\CD4 ===> [BG2]\CD4
You now have a Full install.