Hard disk prolem'

Have a seagate HDD of 40GB. It detect in the bios, but not in any OS

If your HDD is being detected in BIOS then I'd suggest you to make it Primary master and install an operating system and try to boot through that HDD. I think that you intending to use this HDD as your pen drive. If this is the case once your HDD has booted after installing software and you can't loose the memory dedicated to the OS you can try formating it on different PC because once it is bootable It will deffinetly be recognised by other Operating systems. Note that HDDs formatted with NTFS will only be detected by Windows. HDDs formatted by MAC will be detected by MAC and likewise for linux also.

Probablel corrupt partition. Please advise which OS you are using. In windows you can access the drive from disk managerment from where you can re-partition and format it. Keep me posted