It's well known since MS invented the registry and left older ini-file concept that you never ever install non-Windows-stuff on C: drive under the ruling of Windows. Especially no application software, only exeption may be system software like printer drivers or such stuff. Best possibility divers drives or for one drive partitioning it ... best C: only system, D: for application and E: for the data as such. Even a very good idea for backup handling C: and D: are only urgent if changng something but E: need a fix turnus. OK, since in software development a permanently renovation of their "green" stuff (banana ware) is up-to-date even C: and D: needs more often a backup but not day by day.

If multi drives or partitioning is not suitable the second best idea is to have on C: a directory besides the Windows stuff like "AllMySoftware" and install all application stuff in that. Such a directory is outside of Windows control and therefor no UAC trouble. B.t.w. running stuff outside of the Windows directories is also bringing a win-question if you want to do so but isn't disturbing file writing in that locations. And the win capabilities to save against maleware writing are even rather unsave. So no need to cope with the MS restrictions to much.

Have had for years to maintain users pc's which was setup by dealers according to the MS guidelines and its only a question of time that those pc's are gigantic rubbish graveyards and the user have no space and also not finding anything back again (secretary around 6 month, normal office clerks 1 to 1,5 years, chiefs up to 5-7 years ). Round about 2-5 hours work for the maintance guys and dolls to clean up one pc depending on how much sensefull stuff is hidden between all the temp and such rubbish ...