As of today there are no 64-bit installers for Blender 2.49a
At first I thought maybe they hadn’t come around to it yet and I just waited but, now it’s been quite a while and… to be honest I’ve come to the point where if I knew how to do it, I would already have.
Unfortunately, I have no idea how to build an installer for this. 
i assume you eman the windows installer. you dont really want it. i’m 32 bit and used to use the installer because it was “easier”. actually it’s not. the installers default is to split the program into different folders which makes it a pain in the butt to add scripts or anything else. it is uch easier and quicker in the long run to download a zip, unzip it to c:blenderXXX (XXX= version number) the same as python, right click on the blender exe and create a shortcut to desktop for a quick launch. then rather than having to hot start, all programs, blender you just click on your shortcut. you can also have multiple bleender versions installed. then you know where the folders are, they are where they are suposed to be rather than in a hidden file you have to change systems settings to show hidden files and folders and track it down to put in new scripts. showing hidden files and folders also makes it much easier for someone sueing your computer to crash it such as changeing required os files. i could use the installer, i dont. i used to, i quit. you started blending in 2006, you know who to get full functionality without the installer. trust me you are already doing it the way you will go back to. (and probably hire a witch doctor to put a curse on the installer.) the installer is like your ex girlfriend…they seem like a dream untill you are stuck with them then they turn into a nightmare, and are an ex once you learn the truth.
I’ve been waiting for an installer for 64bit as well.
Every other piece of software I use installs the program files into the program files folder and the data and settings files into the users home folder, this works well. Is it to much to ask for Blender to work like almost every piece of software?
There has been a 64bit version of Blender for while now so I don’t why there is no installer, maybe there is a technical reason which makes it very difficult.