External HDD can not be detected.

Hi,
a while ago I dropped my external HDD of size 90GB, and since then I was enable to access any data on it.

but, last week, I found it, and just for fun plug it my office pc, and it worked just fine, like nothing had ever happen before, I could directly play, copy movies. music and all.

but now, after I kept it connected, for more then 2 days, I have lost it, my XP pc can’t detect it any more.

any suggestions??

p.s : I have already connected a extra power supply, and wait for XP to detect it for hours..