Why does WinRAR do this? Strange behavior...

I have WinRAR 3.71 on an older P-III desktop with 512 meg of RAM and 100 gB of disk space. Wind XP Pro all up-to-date. I have created with WinRAR a multi-part RAR set consisting of 36 - 100 mB parts with "slack" shoved off to part 36. This is an ISO of a training movie DVD that I own and that I want to preserve to the hard disk for viewing and backing up etc. etc.

When I tried to extract it back into an ISO (different folder and so forth), WinRAR barfed with Packed data CRC failed messages on parts 3, 5, 7, 9 and 11. Notice the odd numbered sequence. The very next move I made was to "Test" that very same RAR set. On the test, WinRAR barfed at parts 1, 3 and 4 - completely different test results versus what WinRAR reported on the extraction.

Interesting experiment: I took those same 36 segments and copied them over to my other (more powerful) desktop (AMD64, 3200, with the same software compliment). WinRAR 3.71 reported no problems on the test. I didn't bother to extract it at that point.

I have generally noticed with this version and most previous versions, that multi-part RARs that are, say, less than 7-8 parts seem to work fine with this version. But anything containing parts greater than 7-8-10 the results are quite often met with "Packed data CRC failed...".

I don't understand why the difference when both an request for extraction and a request for a test should come out the same. I notice there are some "Advanced" settings that I've never played with. Are these important to help resolve these rather cryptic "Packed data CRC error" issues? And, yes, I realize I'm on an older machine but I don't believe this should be an important enough issue. Some may not agree, but my feeling is that if the software launches it really should run.

I'd appreciate some insight into this. And what about some of those advanced settings? Anyone got some ideas on how to set up WinRAR for a more successful output given the hardware I'm using?

Thanks folks.