hello Everyone

I purchased a second hand dell inspiron n4050 from a second hand store Cash Converters, but unfortunately when I got it home, when I turn it on, I get no further than a split second before it jumps up with this message:
Service Tag : H4DTGP1
Enter System Password
Please type in the system or administrator password and press <Enter>
I went back to the store but they said the password was not on when they showed me the laptop in store, I don't know if it was or not? because they turned it on, then showed me it working. They also refuse to take it back, or give me a refund, but said for $90 they could get it fixed

Wow! I just paid $190 for it, now they want $90,before I can use it
Anyway, after searching without success, I came across your site, and I hope you can help. I'm a disability person, and cant afford to give away money like that, I feel cheated

Reading other posts, I can give you the service tag and express service code:
Service Tag: H4DTGP1 Express Service Code: 37270374085
I did call Dell, but they said I needed the original owners details, How am I supposed to do that, it could be anyone?