Verify Failed error/CRC errors

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crickplayer
Posts: 5
Joined: Sun Feb 14, 2010 11:36 am

Verify Failed error/CRC errors

Post by crickplayer »

since yesterday any file that I download ends up either giving me verify failed error or crc error when it tries to unrar. This happened with about 4 files I downloaded, all over 4gb each.
alex
Posts: 4514
Joined: Thu Feb 27, 2003 5:57 pm

Post by alex »

it might be antivirus or memory issues (antivirus more likely since if memory is bad it will also may well cause program/system crashes).

if it sometimes succeeds to repair it means the rar is ok, so if unrar or winrar fails later means some weird interference.

but also try to test memory if the database is relatively small and only a bit or two failed somewhere the probability of crash may be low.

just yesterday i got random windows crashes on start or some time after start on a computer here because one memory stick out of two suddenly went defective after many years working ok, but it was pretty apparent that something is wrong with hardware. you can also remove one stick at a time to check if it is memory.
crickplayer
Posts: 5
Joined: Sun Feb 14, 2010 11:36 am

Post by crickplayer »

how can i test if its because of memory?

just finished downloading another two files and what i get is Repair: Verify failed error.

it says 63 of 71 files. so i'm guessing its missing files, how can i download those files?

for the other file it says 49 files Repair: Verify failed error and then if i try to unrar it, i get crc error or wrong password.

all this started happening yesterday. can it be my connection?
alex
Posts: 4514
Joined: Thu Feb 27, 2003 5:57 pm

Post by alex »

Repair is a mathematical operation like matrix multiplication, so normally it cannot fail (the same unlikely as if would get 2*2=5 when using windows calculator).

So it may fail on disk write operations, e.g. UE writes into disk and some e.g. antivirus software in the middle scans the files on fly, but because of a bug it also corrupts the data so what is written is different.

Or, second reason, if memory is defective (e.g. even one bit doesn't work) and the memory is used during repair to keep the matrix data it will 100% will cause repair error.

If you are sure nothing has changed on your computer as to software (e.g. some automatic antivirus update), you can run memtest.

http://www.netwu.com/newspro/MemTest.zip

It is an old program and it has some limit (maybe 1.2GB to 1.4GB), if you have more RAM you can run several instances simultaneously, don't run other programs so the RAM will be available. Or you can run some other memtest program.

Another way, since it is so easily reproducible, if you have several memory sticks, you can remove one memory stick at a time from your computer, possible rearranging the others to get valid BIOS RAM configuration (while the computer is off :) ), if it works with a particular memory stick removed it means it has failed. But try memory test first.

Are you sure it is not antivirus interference? Another way to cause repair errors is to run QuickPar repair concurrently.
Josef K
Posts: 534
Joined: Thu Feb 27, 2003 7:29 pm

Post by Josef K »

alex wrote:If you are sure nothing has changed on your computer as to software (e.g. some automatic antivirus update), you can run memtest.

http://www.netwu.com/newspro/MemTest.zip

It is an old program and it has some limit (maybe 1.2GB to 1.4GB), if you have more RAM you can run several instances simultaneously, don't run other programs so the RAM will be available. Or you can run some other memtest program.
Rather than that, go to the Memtest website itself and download a prebuilt ISO, burn to CD and boot from it and it'll run continuously until you stop it. It'll also be the latest version, v4.00 which will test the full range. I regularly test 4GB. In the BIOS, disable Legacy USB before testing with Memtest, you can re-enable it after you're finished testing. Make sure you have a PS/2 keyboard around in case anything 'interesting' happens if you do this using a USB keyboard.

I would also recommend testing one stick at a time and if any errors occur, also try moving them to another slot to rule out motherboard DIMM slots going bad. This can happen after, for example, power supplies going bad, motherboard shorts, power surges, etc. but it does happen.
crickplayer
Posts: 5
Joined: Sun Feb 14, 2010 11:36 am

Post by crickplayer »

So I downloaded the program from http://www.netwu.com/newspro/MemTest.zip and tested 1000MB. The program stopped about halfway saying Memory corruption detected. I'm using a laptop with ddr2 memory. the laptop has 1 stick of 2gb of ram. Since that program said my memory is corrupted, how can I fix it. I didn't change anything on this laptop. i.e install anti virus programs or firewalls. I only use this laptop for downloading and i'm just wondering how can the memory all of sudden go bad. i'll also try what josef k said in a bit and see how that goes. would formatting the laptop fix this problem? if so, i'd rather just format the laptop.
crickplayer
Posts: 5
Joined: Sun Feb 14, 2010 11:36 am

Post by crickplayer »

this seems to be the problem with large files. i downloaded a few files under a gig which seemed to work.
Josef K
Posts: 534
Joined: Thu Feb 27, 2003 7:29 pm

Post by Josef K »

The memory that is bad is physical, that is, you cannot fix it through any other means than by replacing the memory stick itself. Why it happened you may never know. It could have been bad from day one but only appeared recently, for example, if you only just started downloading certain files of a large enough size. The same behaviour can be seen where you can browse the web, check emails - light use - but then you will see crashes once you start playing games which will be much more memory intensive, although it can happen anytime.

One thing I would suggest is to run the test a few times. With Memtest it is always recommended to run it for as long as you can, usually overnight is more than good enough. The newer version I mentioned would be the better one to use since it has better hardware detection capabilities and so should not be influenced by incorrectly detected hardware.

If it comes to having to replace the memory, once you get a new stick you should immediately run Memtest on it. You will then be in a better position to verify it works and the sooner is always the better if you need to return it for a replacement if it's bad. Remember that with memory, even one single error is unacceptable.

P.S. I just had a look at the Memtest that Alex linked. It's a different program to the one I linked although going by (almost) the same name. The one I linked is actually called Memtest86+ and you'll find many references to it just by searching for that name. It's pretty much the gold standard for memory testing software. You should run the version I linked because you can boot from the ISO and it will test the entire memory range outside of Windows. Running outside of Windows ensures that your problem isn't caused by Windows itself or, as you mentioned, antivirus or a firewall. If you have no CD drive, you can boot it from a flash drive.
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