Replying to External hard drive problem

hey guys,

im finally making the change for the good. tomorrow im buying my first mac (macbook pro). today I was sitting at my desk on my comp and i noticed the box for my external (which ive had for awhile). it made me curious if it would be compatible with my new mac. i looked at the box to find that it said "Works with Windos XP and Windows 2000". this made me panic. dropping all this cash on a new comp. i dont have the money to buy a new external. all our footy from the past 2 years is on it.

i thought back and realized when we tried to plug it into my buddies MBP earlier in the winter it didnt work. we did nothing special, just plugged it in and tried to access it. but it didnt work. i dont remember the details but i remember it DID recognize the drive and it was clickable as if you could access it. long story short.... it didnt work. we didnt really try hard to make it work since the files we wanted to transfer were easily sent on AIM.

I figured id ask here since all of you guys seem to know quite a bit about macs.

so my question is:

is it somehow possible to use or configure an external hard drive on a mac that has been used on a PC?

i really need this to workout as it would save me time and money such as buying a new external.

thanks for the help guys!

e williams