Uh Oh 
So I recently upgraded from XP to Win7, got round to loading up Steam, asked for the password and I was sat there manically typing any number of possible passwords it could be with no success at all. I went through the security question only to be given "What did customer service reset your password to?".... uhm, they haven't
. So at this point i start typing any of my passwords it could have been. Spent about 10 minutes doing lots of different combinations before i decided to see what other routes I could go down.
A quick google revealed a support ticket with proof of purchases will do the job. Now at this point I can't get any CD Keys, so I booted up my laptop, only to find that steam has the password saved and it logged on just fine :/ this confused me, but I carried on as it allowed me to printscreen some CD keys and a print screen that I was once on the account. I also included in ticket my credit card type, the expiry date, my name, and the last 4 digits. With a nice summary of what had happened with politenesses at start and end.
6 Hours later (which I don't think is too shabby) I get a reply...
"Sorry, you will have to create a new account and re-purchase your games"
lol only joking, this was the real reply
"Hello Doogle, Thank you for contacting Steam Support. It appears as though the account may have been hijacked by another user. Please follow the link below and take the prescribed steps to ensure the security of the account in the future. I have reset the account password and sent the new login information in a separate e-mail. If you do not receive the e-mail and you are running a Spam filter, check and make sure the e-mail is not being filtered as spam. Note: Passwords are all numbers. The new Secret Question will be set to "What did customer service reset your password to?" The answer to the Secret Question is the new password that we have sent to you as mentioned above. Once you login to the Steam Account, please change your password, secret question and validate your email address. Please let us know if we may be of further assistance."
Got the e-mail with the new password, changed to something i will remember and numbers and characters and capitals, changed the security question, and re-verified my e-mail address.
So I was happy with the outcome, however I do find it a bit peculiar that my laptop would login, yet no password I have ever had would work and steam reckons it was hijacked?
Mainly posting this to raise awareness of account security, to show that you can probably always get your account back if you do own it, and to read your theories on what you think happened.

So I recently upgraded from XP to Win7, got round to loading up Steam, asked for the password and I was sat there manically typing any number of possible passwords it could be with no success at all. I went through the security question only to be given "What did customer service reset your password to?".... uhm, they haven't

A quick google revealed a support ticket with proof of purchases will do the job. Now at this point I can't get any CD Keys, so I booted up my laptop, only to find that steam has the password saved and it logged on just fine :/ this confused me, but I carried on as it allowed me to printscreen some CD keys and a print screen that I was once on the account. I also included in ticket my credit card type, the expiry date, my name, and the last 4 digits. With a nice summary of what had happened with politenesses at start and end.
6 Hours later (which I don't think is too shabby) I get a reply...
"Sorry, you will have to create a new account and re-purchase your games"
lol only joking, this was the real reply
"Hello Doogle, Thank you for contacting Steam Support. It appears as though the account may have been hijacked by another user. Please follow the link below and take the prescribed steps to ensure the security of the account in the future. I have reset the account password and sent the new login information in a separate e-mail. If you do not receive the e-mail and you are running a Spam filter, check and make sure the e-mail is not being filtered as spam. Note: Passwords are all numbers. The new Secret Question will be set to "What did customer service reset your password to?" The answer to the Secret Question is the new password that we have sent to you as mentioned above. Once you login to the Steam Account, please change your password, secret question and validate your email address. Please let us know if we may be of further assistance."
Got the e-mail with the new password, changed to something i will remember and numbers and characters and capitals, changed the security question, and re-verified my e-mail address.
So I was happy with the outcome, however I do find it a bit peculiar that my laptop would login, yet no password I have ever had would work and steam reckons it was hijacked?
Mainly posting this to raise awareness of account security, to show that you can probably always get your account back if you do own it, and to read your theories on what you think happened.