Carefully check the drive type - most are parallel ATA, while some are Serial ATA.

You can go to 120G if parallel ATA.  Serial ATA is unlimited.

Pull the drive out.  If it looks like the connector is a long, thin strip, it's parallel ATA.  If it has  two small connectors, it's serial ATA.

Most 9300s are parallel ATA.

Any standard, parallel ATA drive, 120G or smaller, 2.5"/9.5 mm can be used.

I haven't noticed any problem with the 120 GB limitation .... I'm running a mixed Window/Linux environment without any problem. The drive is a WD2500BEVE, my BIOS is version A05.

Disk /dev/sda: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1       13055   104864256    7  HPFS/NTFS
/dev/sda2           13056       30395   139283550    f  W95 Ext'd (LBA)
/dev/sda5           13056       14386    10691226    b  W95 FAT32
/dev/sda6           14387       15661    10241406   83  Linux
/dev/sda7           15662       16438     6241221   82  Linux swap / Solaris
/dev/sda8           16439       30395   112109571   83  Linux

Stay tuned. If it hasn't fouled up yet, that doesn't mean it won't eventually. I also have a 9300 that I upgraded from a 100 gig PATA drive to a 250 gig WD Scorpio like yours. I did everything I could to protect it via the latest bios upgrades and Windows XP SP2 drivers, even using the Ontrack DDO. However, last weekend I found myself staring at a blinking cursor instead of a booted up lappy.

I thought it must have been the Master Boot Record or similar corrupted, but it wasn't. The only way I could get the thing to boot up again was to load the drive into a USB caddy and then use Acronis Disk Director (on another PC) to resize the partition from 250 gig down under 137 gig.

Lesson learned. PATA isn't SATA with a P.