Windows 7 Professional Product Key Invalid for Activation

First of all, apologies if this problem has been posted before and solved - I did look but I couldn't find it.
Second of all, I know next to nothing about computers and wouldn't have them if I didn't need them for college work. Because of that, I don't know what information you might need to know - so I'm just going to put everything I can think of!

I have an HP Pavilion g6 laptop that I have had for several years. Around Christmas time the hard drive died and I had to get it replaced. That all went fine except for the fact that I'm from England (where I bought the computer) and at that point I was on in Canada. Obviously I didn't think to bring my windows disks with me. And I wasn't going back to England any time soon. The tech guy who replaced my hard drive told me it was no problem and put Linux on the laptop so I could use it until I could get my windows disks. Or I could just keep using Linux.

As I was traveling around, I didn't have an address to get anyone to send my disks to me until a month ago, when I settled in Mexico for a while. My father bought me new Windows 7 disks from the US as they would get to me quicker.
I managed to figure out how to partition my drive and everything so that I was able to install windows without removing Linux (as I couldn't find out how to do it any other way. No one seemed to understand why I would want to remove Linux!). Everything installed correctly except for the fact I wasn't able to get online to activate it. I typed in the windows key and selected the option to activate next time I was online. No big deal, I thought, I had a month to find an internet cafe.

Well, now I am finally online (past the activation deadline) and trying to activate windows and it keeps saying that 'The Windows 7 Professional product key you typed is invalid for activation'.

I thought perhaps I had just typed it in wrong and went to re-type it but the ink has worn off the stupid little sticker they sent you so now I can't read it! Seems like a major design flaw to do that after only a month.

I don't have a cellphone (I don't like them either - hard to believe I'm 22 sometimes) so I can't call Microsoft, so I'm really hoping this is something I'll be able to fix online.

Is there anything I can do or do I have to scrape together the money for another windows key?

Thanks in advance for any answers!

This might seem roundabout but doing a System Restore to a point within the 30 day limit would work to allow you to activate. Wherever you are, it might pay to just pay the heavy toll to call MS to activate and some 3rd party phone services offer cheap rates if you have access to any phone.

Sorry, I didn't make it clear in my original post. I tried to activate it 2 days ago (within the 30 day period) and it wouldn't do it then. I assumed it was because of the slow internet and decided to try again next time (today - out of the 30 day limit) so unfortunately I don't think that will work.
I actually think it might be cheaper to buy a new product key than phone MS - unless anyone knows if it something they could fix quickly.

I can't answer about what a call wopuld cost but MS would solve the problem.

If it's a valid key, the call to MS is free. I own two retail packs of w7, one I never have problems installing, the second, originally purchased when I built my my wife's computer always has to get called in.

The phone number in Mexico is +52 (55) 5267-2000. I can't vouch for the cost of the call because Telmex can be expensive but, the Microsoft validation is free.