ok, recently, my main HD has died, but as a good boy I did backup for everything. I buyed a new HD, copyied everything from my backup to the new HD.

Then I tried to boot my old system on the new HD, everything goes fine until I got e2fsck :
FSCK 1.27 (8-MAR-2002)
/sbin/e2fsck : filesystem has unsupported feature(s) (root)
e2fsck: got a newer version of e2fsck

Ok, at this point, I remembered I had tried something different about my fs : I added a Label!
So with tune2fs, I erased this label...
now the msg I got from e2fsck is :

FSCK 1.27 (8-MAR-2002)
/sbin/e2fsck : filesystem has unsupported feature(s) (/dev/hda1)
e2fsck: got a newer version of e2fsck

WHAT'S THAT? Well, e2fsck, if you don't know what's /dev/hda1, you (and I!) have a serious problem.
Now what did I'm suppose to do? Is it really a e2fsck version problem (this look impossible, the LABEL is supported since twenty years, at least)?

Can it be because my new HD isn't the exact size my old one was?

(oh well I suppose recovery will never work perfectly )

I buyed a new HD, copyied everything from my backup to the new HD.
To determine what's really dumb, did you copy disk contents, or did you "dd" the whole disk?

I copy the whole disk content with cp... you know, cp -a, seems to have worked well, except with that little e2fsck problem... I think I'll do a new installation of Slackware 8.1 THEN transfert everything using cp... it should works better I suppose.

why don't you try to reinstall fsck first before you blow away all your hard work.

...or try fsck from something bootable like tomsrtbt?

I think that Half_Elf's problem has to do with the version numbers in e2fsck and mke2fs. Half_Elf probably used a newer version of mke2fs to create the new disk. e2fsk has a check to make sure that it is running against a file system created by a mke2fs version equal to or older than itself. It refuses to work against a file system created by a newer version of mke2fs.

Therefore the solution to Half_Elf's problem is probably to install the latest version of e2fsck.

ok... then I will have no choice to "blow away my hard work" since nwer version of e2fsck need glibc 2.3 (and this system is currently using 2.2... and you know habitually, updating glibc under slackware result on a disaster, well last time I tried it).
Thank you for all your answer... I'll know for the next time.