Afaik you have 3 choices.
1) Buy C&C First Decade (and ofc that will cost you) since it's installer has no problem running on Vista or Win7.
2) Use a little tool called Red Alert Manager which you can find here
(scroll down). What it does is it patches the exec so that it can be run under Vista (I've successfully used it to install the game some months ago on Win7 RTM so it should work with a retail Win7)
3) Manually trick the installer into thinking you're running Windows95.
To do this you need to run the setup exe directly from the disc in Win95 compat mode (don't use the autorun). Then to play the game you just have to use the XP Compatibility Patch made by EA. You can find this one here
Then just play the game in XP compat mode.
Hope this helps.