Mount encrypted volume before / during login

Question

To reduce impact of possible computer theft, I would like to have my user profile protected using a robust encryption, so that even if someone can get a physical access to my computer, he will not be able to read my data.

I am running Windows 7 Professional.

As I understand it, Windows 7 user profiles are not secure against an attacker having access to the system, as he is easily able to boot the system with another OS disk to get administrator access to the system.

I know one option could be to upgrade to Ultimate edition to use BitLocker, but upgrading seems difficult, as Anytime upgrade is not working in my country and one needs to find a retailer who would still be selling Windows 7 upgrade. I would therefore prefer to find a 3rd party solution.

Another possibility would be to use TrueCrypt to protect the whole system partition, but that seems a bit extreme to me - I would need to repartition my disk to provide a new unencrypted boot partition, and I am also not quite confident what might be the performance impact of such solution, or how well would TrueCrypt play with the RAID 1 I am using on my system disk.

What I am looking for is something which would protect my user profile, but nothing more.

What I have found some far is a possibility to mount a TrueCrypt volume before login, however this has a serious drawback: the password is stored on the computer, therefore it does not fit intended purpose of protecting the data in case of the computer theft.

Is there any solution for this? I would prefer Open Source solution, but I do not exclude a commercial one if it works really well.