Right well, i have tried installing 4 different OS's (formatted before each). I have tried installing
Windows 2000 Professional
Windows 2000 Server
Windows 2000 Advanced server
Windows XP Professional edition

The CD's are all fine, as i have tested them on another machine. The HDD is also working properly. I have tried using the "fixmbr" utility from the XP CD and the Windows 2k Pro CD, with no luck.

I have disabled the onboard virus protection, didn't help either.

Basically, the problem is that after the setup finishes formatting, and then copying files it is supposed to restart. Well it restarts, and when it is supposed to continue the setup from the files copied to the HDD, it says "error loading operation system".

The HDD has had Linux installed on it before, not sure if that matters. I have deleted the SWAP partitions and everything and done a complete format so that shouldnt effect it.

The system has worked fine about a year ago with Windows XP Pro installed on it.

It has 512MB of SDRAM and a 1.15Ghz AMD Athlon protsessor. The Motherboard is some old type of ViaTech or something like that.

Any help would be appreciated, and if you need any additional information feel free to ask.

Thank you in advance.

...why you want to take out Windows XP Pro? If it work fine, leave as it is. Have you considered to use the Windows 2000 and XP Setup (FDISK is included by automatic, all you have to do is just select either Format quick or Format as NTFS)

If no luck, a suggest for your last sake

Take that problematic hdd out and install it as master in other machine, run the installation wait until it finish and have the last reboot, shut it down before it start the windows xp for first time, then install it in your old pc.

I'm afraid you didn't understand a thing i said.

I am not removing Windows XP, i can't install ANY OS on the system. I have tried fdisk and fdisk /mbr

Ah i apologize, can you try install your hard drive on other computer?

Not that easily to be quite honest. The second machine i have, is used to host a gaming server for a game called Legend Of Mir. To install the HDD on the machine i would have to shut the hosting machine down which i cannot do right now. Is there any other possible solutions?

Windows is rather picky about partition tables. The machine had Linux on before, so the bootsector may not be quit what Windows expects. Fix that by writing zeroes to the beginning of the drive drive. Either use the dd command in Linux (something like "dd if=/dev/zero of=/dev/hda bs=1024 count=1024") or some disk wiping utility (let it run up to 1% or sth similar).

Downloading Norton GHOST right now. Hopefully it is not another "fake" which doesnt boot.

I also thought, could it be a problem that i am using a weird/faulty IDE cable for the HDD? At first i used another cable and got a "no 80 connector pin" or something similar error, then switched the IDE cable with another one (old) and i didnt get the error anymore. Could it possible have effected the connector on the MB or anything like that?

Norton GHOST didn't help, nor did maxtors low level format (yes the HDD is from maxtor). Any more ideas :/?

No, the IDE cable thing doesn't matter. And if you had a faulty cable/controller/disk, then the problems would more likely show while copying the files to the disk, not when rebooting.

In BIOS, try changing the hard drive access mode. You have a choice between AUTO/NORMAL/LARGE/LBA or something similar. AUTO and LBA are good choices, but you can try others.

You have actually set the boot order in BIOS so that the hard drive is in there somewhere, right?

I have tried changing the access modes already without luck ><.
Yes, the sequence is
1. CDROM
2. HDD0

I also tried changing it to
1. HDD0
2. CDROM
Right after it reboots to run the setup from the HDD.
Yes the HDD is primary master.

try this. it works:
get a 98 floppy boot disk from here
start your pc with boot disk in the machine
after win98 comes up, enter fdisk
display partition(s) (if any)
delete partition(s)
create new partition
restart
format the hard disk
turn pc off
take win98 boot disk out
put xp cd in the cd rom drive
turn pc on
get into bios
go to boot sequence and choose "boot from cd first"
save bios, exit.
let xp install.