Just tested a couple of more games I have lying in my shelf. This is on a 64 bit Windows 7 RC1 client, but it shouldn't make any difference from the full version.
Heart de Roommate (CD): Works. Starting the game from the CD executable/autorun will cause the game to crash when you try to start a new game, also the main screen music does not work. Starting the game from the harddrive solves both of those issues. Same boxed look in full screen as Private Nurse (again, might just be an Nvidia thing, I can't test that).
Kana - Little Sister: Installer crashed after completing the copy process, but starting the game from the harddrive normally worked just fine. Music and video works, full screen worked properly (but intro video was horribly pixelated, in-game it was much better).
Kango Shicyauzo (Voice Plus, CD): Works, but was already installed so I can't test if autorun from the CD is borked like with Heard the Roommate, as it was installed on my XP partition so there's no registry info for it (hence manual executable start required). Full screen gets the same box look as Private Nurse and Heart de Roommate, otherwise it seems ok.
Kango Shicyauzo 2 (CD): Works, boxed full screen look. If you have the same CD version as me, remember that something went awry in the disc pressing and the CD check info is actually on the INSTALL disk. So in order to start the game, when it tells you to insert the game CD, you need to insert the install disk instead, then after it repeats that it wants the game CD, swap them. Then it works.
Tokimeki Check-in! (CD): Works. Installer took a long time to start, might just be my CD though. Full screen looks ok. Game is EXTREMELY sluggish unless you disable music or switch to the CD-DA one that is on the second CD. On a side-note, when I picked CD-DA and it told me to insert the second CD, Winamp came up and started playing an MPG file that was on the second CD with an advertisement for Brave Soul all by itself >_>. Also, after you've switched to CD-DA, you can swap back to midi and the game will behave normally (and play the midi music) until you enter a different area (or something else happens, didn't test much) at which point it will be sluggish again. Not that I can think of why you'd want to play midi instead of CD-DA music.
Come See me Tonight (CD): Works. Boxed full screen mode. Annoyingly, it seems that somehow music and voice volume in this game is somewhat connected, so you can't really make voices louder while at the same time making music quieter, since lowering the music slider affects voice volume as well, even if you crank up the voice slider to max. So in some cases it's pretty hard to make out what some of the more quiet girls are saying over the loud music. I seem to recall having this happen in another eroge too though, but I can't remember which one. In any case it might be unrelated to the OS. There's also a slight delay between music tracks where the game seems to hang a little bit, but it's not really a big issue.
Tsukishite Agechau 4 (CD): Works. Boxed full screen mode, yadda yadda. Same voice/music slider issue as Come See me Tonight, so I think it might be a generic G-Collections title thing (as the two games are from different Japanese developers), or at least prevalent in multiple of their titles. Intro music (after you've returned from the US Lab) doesn't play unless the game is minimized and opened again or the screen moved around a bit.
Anyway, that's all I had time to test tonight, got work in the morning.