So these are the main characters, the 200GB drive is detected as 33 (or so)GB drive by the BIOS. When I loaded the hard drive in windows (allowing it to make its partition), it read it as a 200GB drive despite of the BIOS. When I formatted for reiserfs, same thing, but now Windows sees it as unformatted 33GB.
I have the latest BIOS for an asus a7v8x-x.
So the problem is that once in a while this disk throws the error I will show you in the dmesg, and I can see all the files but not open them.
When that happens, my only choice is to reboot the pc (sometimes it takes days to happen, some times much less time). The HD is almost new, so I doubt it has any broken sectors.
Thanks a lot for the help, here's the log

Welcome to LQ!

You didn't include the log. I can't exactly understand what you've got from your post.
A couple of things I can tell you. First, Windows cannot "see" a reiserfs partition.
Second, you can get a bad hard drive straight from the factory. You should get the
diagnostic tools from the manufacturer of your hard drive, and run the test to check
the integrity of that disk. I've built computers for a number of years now, and from
time-to-time I have found a brand new hard drive to be defective. In fact, I had a
new Western Digital that was bad in a box I built in August.

In addition to the dmesg output, please include the output of:
/sbin/fdisk -l
cat /etc/fstab
df -h

ha, you're right, I forgot the log.
Anyway, I know windows does not read reiserfs, but it should see it as unknown partition, not unformatted.
I think window's LVM could have some fault on this, as it doesn't detect the correct size of the drive either.
anyway, the relevant dmesg is:
ide: failed opcode was: unknown
ide0: reset: success
hdb: task_in_intr: status=0x51 { DriveReady SeekComplete Error }
hdb: task_in_intr: error=0x10 { SectorIdNotFound }, LBAsect=225723503, high=13, low=7619695, sector=225723503
ide: failed opcode was: unknown
end_request: I/O error, dev hdb, sector 225723503
ReiserFS: hdb1: warning: vs-13070: reiserfs_read_locked_inode: i/o failure occurred trying to find stat data of [18138 18176 0x0 SD]
A lot of those each time it fails.
THen fdisk -l
Device Boot Start End Blocks Id System
/dev/hda1 * 1 10943 87899616 7 HPFS/NTFS
/dev/hda2 10944 10947 32130 83 Linux
/dev/hda3 10948 11009 498015 82 Linux swap / Solaris
/dev/hda4 11010 14593 28788480 83 Linux

Disk /dev/hdb: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/hdb1 1 24321 195358401 7 HPFS/NTFS

Relevant HD here is hdb1
fstab
# <fs> <mountpoint> <type> <opts> <dump/pass>

# NOTE: If your BOOT partition is ReiserFS, add the notail option to opts.
/dev/hda2 /boot ext3 noauto,noatime 1 2
/dev/hda4 / reiserfs noatime,user_xattr 0 1
/dev/hda3 none swap sw 0 0
/dev/hdb1 /media reiserfs noatime,user_xattr 0 1
//192.168.1.102/share /home/sdistefano/notebook smbfs noauto,users,exec,uid=1000 0 0
//192.168.1.101/silvio /home/sdistefano/roberto smbfs noauto,users,exec,uid=1000 0 0
#/dev/fd0 /mnt/floppy auto noauto 0 0

# NOTE: The next line is critical for boot!
proc /proc proc defaults 0 0

# glibc 2.2 and above expects tmpfs to be mounted at /dev/shm for
# POSIX shared memory (shm_open, shm_unlink).
# (tmpfs is a dynamically expandable/shrinkable ramdisk, and will
# use almost no memory if not populated with files)
shm /dev/shm tmpfs nodev,nosuid,noexec 0 0
#/dev/hdd /media/cdrom auto user,exec,noauto,managed 0 0
#/dev/hdc /media/cdrecorder auto user,exec,noauto,managed 0 0
and df -h
Filesystem Size Used Avail Use% Mounted on
/dev/hda4 28G 21G 6.8G 76% /
udev 252M 2.5M 249M 1% /dev
shm 252M 0 252M 0% /dev/shm
/dev/hdb1 187G 104G 83G 56% /media

There would be no problem if the HD is faulty, as it is still covered by warranty, but I want to make sure is that and not some BIOS/software problem.
Again, thanks a lot

Short on time right now, but that output is quite confusing. You have:
You can have an incorrect label (which it looks like) on the partition,
and can change that easily with "cfdisk" or "fdisk" if you prefer.

To expand on Chinaman last thread the reason windows is seeing /dev/hdb1 is because the partition ID is 7 and not 83. Since windows can not read the filesystem it assumes the partition is unformated.

Check the hard drive to see if the 32GB jumper is installed. This is used to trick the BIOS of older PCs that can not handle larger capacities. The actual info is read from the drive itself and not the BIOS so that is why linux can see the entire space.

I also agree with Chinaman that the drive might be failing. Check it out with the diagnostics software.