I've been getting a few e-mails from people asking where they can download MSE now that Microsoft have closed off the beta. The short answer is I don't know.
I can tell you the MD5 and SHA-1 hashes, so you can at least make sure you can get a copy that hasn't been tampered with if you're that keen on using it.
There's three installers:
mssefullinstall-amd64fre-en-us-vista.exe (3.72MB) which is the installer for Windows Vista and Windows 7 64-bit, its hashes are as follows:
MD5: D460B3A5116FF1DB2CFA69ACA80DF8C0
SHA-1: B5E7FC24FCD646EFCAE3457DB7D7FC48E648AE23
mssefullinstall-x86fre-en-us-vista.exe (4.72MB) is the installer for Windows Vista and Windows 7 32-bit.
MD5: 4C9AC845F5FD5547FC522035FA251F00
SHA-1: 7986596458E37EF8875A9DDAC0AE9AAC9A41E936
mssefullinstall-x86fre-en-us-xp.exe (7.51MB) is the installer for Windows XP 32-bit.
MD5: 7F9D0DE36B6673974D4D6BD6F5731D89
SHA-1: F273DA4CC2EECFBF0C97B2B0701399A20EC5B7AA
So if you are going to go to any lengths to get hold of it, at least get one which hasn't been modified to include any unwanted surprises.