It is possible that the CD may have been scratched or otherwise damaged since the last time you installed the game. Also, if you used a different computer, or just a different optical drive, then some drives are better able to handle errors.
Anyway, A couple months ago someone else had a problem with the sound.rar and wizf.rar files. I never got around to deleting the recovery files from my webspace, so you can use them as well.
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This is a slightly edited version of a procedure in the
problem when installed topic.
[*] Download the file verification and repair program ICE ECC (
homepage): program
with install (695KB) or just
zipped (624KB).
[*] Download the following zipped
ecc file (507KB) and extract it to a folder on your hard drive (such as 'c:\temp').
[*] Make sure the play CD is free from dust or fingerprints, and insert it into an optical drive.
[*] After installing the ICE ECC program (or extracting the zip file to an appropriate folder), start it. Under the toolbar, the top pane will list all available drives. Browse to where you extracted the ecc file (ie double click on the local disk 'c:' then the folder 'temp') and double click the ecc file (or select it and click on the 'Verify' toolbar button).
[*] In the window that pops up, browse to the folder containing the damaged rar files and click 'OK'. In this case, in the left pane of this window you would click on the plus sign next to your optical drive's drive letter, click on the 'disc3' folder to select it and then click the OK button.
[*] Right after you click OK, the window will be refreshed and the title bar changed, this time asking for a folder to place the recovered file. Browse to a folder on your hard drive (perhaps the folder you extracted the ecc file to) where you have more than 251MB free space (or 138MB for just the sound.rar file), select it in the left pane and click OK.
The program will then read the files off the CD, listing blocks (sections of the file) that it can not read. If the damage in the sound.rar and wizf.rar files are limited to relatively small sections, the program can repair the file right away, saving a good version where you previously indicated.
If there is additional damage, the program will list the error 'Not Enough Recovery Blocks' (with a yellow background colour) in the bottom message pane, followed by the fraction of the available recovery blocks (3 at this point) to the total number required. Given the number of blocks you need, you can download one or more of the following files and extract them into the same folder as the first ecc file.
6 blocks (908KB),
11 blocks (1.52MB)
These recovery files can be used to repair up to 1% damage in the 2 rar files, which should be more than enough (let me know if it isn't).
[*] Next redo the verify, by right clicking on the failed 'Verify' task in the middle pane of the program window, and selecting 'Reset task' (or repeat the procedure as above).
This should produce two valid rar files (or one if you don't have a problem with wizf.rar), which you can use to replace corrupt file(s) reported during the install, or to do a manual install.
Troubleshooting Tips (& manual install procedure) 
