External hard drives recognition

Hello,
My laptop (running Windows XP) does not recognize external hard drives plugged via USB. I tried two - a Seagate drive with an external power source and a portable Lacie Rikiki drive powered from the laptop. While a sound signal occurs when plugging either device, no drive letter is shown under My Computer, no drive is shown under Disk Management in the My Computer/Manage menu, and no devices are shown in the task bar under the Safely Remove Hardware icon. In fact, after plugging any of the abovementioned devices, Windows (and Explorer, in particular) simply suspends.
Both devices work well when plugged to other laptops, while Lacie was also checked on my smart-TV - works fine.
Tried to connect other external portable devices via USB drives, e.g. SanDisk flash drive, Canon camera, even my Nokia E90 - these work perfectly fine.
Both hard drives contain a lot of important files, so partitioning and reformatting, I guess, won't suit.
Would appreciate any help on this matter.
Thanks,
Andrey