Hi, again. I have been looking for answers and finally I think I have them. XP install program seems to lack the needed drivers for this drive. My HP restore disk is either defective or does not support the drive and GParted seems to have the same problem. This has led me to wrong conclusions. My X18-M works fine. I have just installed Windows 7 RC from a DVD and everything has gone fast and smoothly. Now I only have to research if my restore disk is faulty or if it doesn't really support this drive. The latter should be strange, because there are 2730Ps with x18-M drives installed from factory (80 GB ones) and I doubt they have different restore disks.
Thanks for your attention.