How do you change boot.ini for an XPe image during build time? The answer is - manually :-(
TD does generate boo.ini for you with the default ArcPath based on what you set up on the Configuration page. It is done by the EndOfBuild event handler of the Base Component that basically contains the Configuration build logic. However, if you plan to play with dual boot or want to change a logo or add some other boot.ini switches you have to modify just built boot.ini manually every time you do a build in TD. This is typically not a big deal but annoying, especially if you forgot to change boot.ini just before you deploy the image.
There was a few requests in the newsgroup for a way to change boot.ini content directly in TD. E.g., this one. For some reason Microsoft hesitated to implement that (I suspect the feature got a low priority) so I finally decided to step in and do something for XPe devs in this area.
Since TD doesn't support plug-in interfaces I could only implement that feature through undocumented CMI interfaces. Moreover, I didn't want to rewrite the Base Component (possible and I've done that once for debugging purposes) I decided to add functionality that allows us to add extra boot.ini switches. After all, we could always change ArcPath on the Configuration settings page but never were able to change, say, boot loader logo (the famous bootlogo switch).
I ended up with a script that I added to my XPeTools package that does what I described above. Via an additional field of XPeTools macro component's settings page you can add extra switches to the default ArcPath of boot.ini.
Note: added boot.ini extra switches are persistent and won't be wiped out when you start another session of TD with the same project (or simply close and re-open the project in TD). This is done the same way as I did that for other components of XPeTools package. They all have some advanced component properties used as a storage for the component functionality required settings.
A screenshot of TD with the boot.ini extra switches page open is attached.