How to resolve external disk drive problem?

I have a Samsung S2 Portable 500gb external hard disk drive. When I plug it into my computer unit (running on Windows XP Pro SP3), the unit doesn’t detect it. The light on my drive just blinks but the computer doesn’t seem to detect it, even if I wait for several minutes (hours even). The drive is working perfectly and the computer detects other external drives, but cannot detect my Samsung S2. Any suggestions/solutions?