From InstallShield Q110636: http://consumer.installshield.com/kb.asp?id=Q110636 :

Because this error has different causes, you may have to check multiple items on your computer.

1. If drive letters have been changed on your computer, re-assign the original letter to the CD-ROM, DVD-ROM, or operating system drive. Follow the steps appropriate to your operating system:

   Windows XP Users

   1. Click Start, and then click Control Panel.
   2. In Control Panel, double-click Administrative Tools, and then double-click Computer Management.
   3. In the Computer Management tree, click Disk Management.
   4. Right-click the CD-ROM or DVD-ROM drive, or the drive that contains the operating system, and then click Change Drive Letter and Paths.
   5. Click Change, and change it to the original drive letter. Click OK, and then click Close.

   Windows 2000 Users

   1. Click Start, point to Settings, and then click Control Panel.
   2. In Control Panel, double-click Administrative Tools, and then double-click Computer Management.
   3. In the Computer Management tree, click Disk Management.
   4. Right-click the CD-ROM or DVD-ROM drive, or the drive that contains the operating system, and then click Change Drive Letter and Path.
   5. Click Edit, and change it to the original drive letter. Click OK, and then click Close.

   Windows NT Users

   1. Click Start, and then click Run.
   2. In the Run dialog box, type windisk.exe in the Open field, and then click OK. This opens Disk Administrator.
   3. Find the letter of the CD-ROM or DVD-ROM drive, or the drive that contains the operating system that needs to be changed back to its original letter.
   4. Right-click the drive letter and select Assign Drive Letter.
   5. In the Assign Drive Letter dialog box, select the original drive letter from the drop-down list.
   6. Close Disk Administrator, accept the changes, and restart the computer.
2. Verify that registry entries do not contain invalid drive letters that might be causing this error:

   Important: The following steps require you to modify the Windows registry. Modifications to the Windows registry, if not done correctly, can cause serious problems to a Windows system.

   1. Click Start, and then click Run. The Run dialog box opens.
   2. In the Open field, type regedit, and then click OK. The Registry Editor opens.
   3. In the Registry Editor, locate the following registry key:

      HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders

   4. In the right pane, note the values in the Data column of each entry. If any value contains a drive that is not correct for your computer, right-click the entry and select Modify.
   5. Type the correct drive letter in the Value data field, and then click OK. For example, if one of the values is "X:\Documents and Settings\Administrator", the drive letter should be changed to a valid drive on the system, such as ?C:\Documents and Settings\Administrator".
   6. Repeat steps 4 and 5 for each entry whose Data value contains an incorrect drive.
   7. Repeat steps 3 through 6 for each of the following registry keys:
      • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
      • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
      • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
      • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
   8. Close the Registry Editor and run the installation again.