This is the help i got from mstation when i had this error.
ok..
i have tried and i got no issues to get it installed..
here's a quick guideline of what you have to do..
download the mssql 2005 express service pack 3 for x64 from
here
then download the management studio for the above sql from
here
you should then be ok and ready since the sp3 is for win7 and it's a 64bit version aswell..
when you try to install you might get some warnings on the components but just hit continue to proceed..
also if you are re-installing it might ask some more information about having more instances of the program on so i suggest to uninstall the other version if you managed to put something on your pc till now..
if for any reason it asks you to set a service account you can use the local system account of a domain account by simply putting your username and password to logon win7.. just remember to put all the other info correctly, especially the mixed mode for allowing the mirservers to connect..
try out and tell me if you get other problems