External Drive problem

Good Day,

i need help in my problem in external hard drive (120gb SATA) this came from an old computer and works fine, but when i insertit in an external casing to become an external drive via USB2.0, it seems that it cannot be detected with the full capacity of the drive it only detects about 8GB or Less, how ever i tried installing it in another computer to test it and it detects the full capacity. what seems to be the problem? why cant i use it as an external drive? and another thing it also happens in the SD card 2GB when i insert it in my memory card reader it detects 2GB but it doesnt show any of its contents. THANKS please help me

specs of my compter:

Computer Type ACPI Multiprocessor PC
Operating System Microsoft Windows XP Home Edition
OS Service Pack Service Pack 3
Internet Explorer 8.0.6001.18702
DirectX 4.10.0.5515 (DirectX 10)

Motherboard
CPU Type DualCore Intel Pentium D 805, 2666 MHz (20 x 133)
Motherboard Name Gigabyte GA-8I865GME-775(-RH) (3 PCI, 1 AGP, 2 DDR DIMM, Audio, Video, LAN)
Motherboard Chipset Intel Springdale-G i865G
System Memory 1536 MB (PC3200 DDR SDRAM)
DIMM1: Kingston K 1 GB PC3200 DDR SDRAM (3.0-3-3-8 @ 200 MHz) (2.5-3-3-7 @ 166 MHz)
DIMM3: 512 MB PC3200 DDR SDRAM (3.0-4-4-8 @ 200 MHz) (2.5-3-3-7 @ 166 MHz) (2.0-3-3-6 @ 133 MHz)
BIOS Type Award Modular (02/21/06)

Display
Video Adapter Radeon X1650 Series Secondary (512 MB)
Video Adapter Radeon X1650 Series (512 MB)
3D Accelerator ATI Radeon X1650 (RV535)

Storage
IDE Controller Intel(R) 82801EB Ultra ATA Storage Controllers
Disk Drive ST3320620AS (320 GB, 7200 RPM, SATA-II)
SMART Hard Disks Status OK

Partitions
C: (NTFS) 100100 MB (66080 MB free)
D: (NTFS) 100100 MB (60382 MB free)
E: (NTFS) 102.6 GB (62.3 GB free)
Total Size 298.1 GB (185.8 GB free)

i tried all of my USB ports and same thing happens, i tried it in other computer it works fine.

never tried reformatting again the hard drive with partition i just reformatted it a couple of weeks again so it kinda fresh, and the hard drive with partition is NTFS formatted and the external hard disk is nts formatted to. one of my friend said to me that my computer is kinda out dated and because of that it cant read or detect hard disk more that 320gb??? is that true???

so what should i do sir??? i just reformatted my external drive still nothing happens.i tried pluggin it in a desktop computer and it detects the full capacity of the drive =( does the problem involves my external casing maybe?