this is a well known and published bug, so it is nothing you are doing wrong. the problem is in the Just-In-Time compiler provided by Sun Microsystems to Oracle - file symcJIT.dll. Intel Corporation first spotted the problem using a beta version of Oracle 817, but Oracle had already gone to press with their CDs and didn't want to do a recall or press new CDs. The problem does not exist on Oracle9i, which uses a more recent and less bugy version of Sun's JIT compiler.
1. copy the contents of the Oracle8i CD to your hard drive's temp folder, then put the CD away.
2. search for and delete both copies of file symcJIT.dll from this temp folder.
3. run the installer from the temp folder.