I got this error every time I tryed installing StormLinux 2000. I dont know why, but for some reason, it wont detect my hard disk. The funny thing is that I had installed StormLinux 2000 previously, and there were no problems at that time.

According to your subject line the error is about opening /dev/hda, this device file points to primary master disk.
The device file /dev/hda1 however points to your first partition on that same disk.
There might be a problem in your /etc/fstab file for instance.

Does your computer start at all?
With boot disk?
If the answer is yes for any of the above, then boot linux and examine /etc/fstab
less /etc/fstab
Is there any row containing /dev/hda?
If yes this might be the problem. Posting your /etc/fstab here might help in finding the error.

No, as I pointed out, it's an installation error. It cant find my hard disk at all. After the first error message, the next one is:"partition 2 isnt alligned to cylinder boundaries". I never got that error before. I think it might be because I played with PQ Partition Magic 5.0(MS-DOS version, not for windows) when I partitioned my hard disk.

I asked a friend about this error and he laso thought that it might be PQ Magic 5 that messed it up. Try a newer version of PQ Magic.

Check ure BIOS for disk settings, might be on NORMAL instead of LBA. If thats so any apps have the wrong translation values for working with the disk.
If it isnt that try installing in expert mode and feed it the CHS info (cylinder, head, sectors).

Ive worked with PM v4 to 6 and it always corrects errors on checking partitions & disks. however, if the translation values from the BIOS arent ok then nuttin can keep the rest from makin a booboo :-]