Talking about DVBDream, its cited on its beta forum:
"Microsoft DID NOT transfer any DiSEqC-commands via Window's-BDA-System ! ! !
This must be done by a turnaround in directly 'talking' to the driver ! ! !
If you may own a TwinHan-Card (e.g. 1041) it may work with my BDA_ALL because i implemented the whole IO-CTRL-Interface to handle DiSEqC, CI/CAM, remote and more.
Also DiSEqC 1.2 is possible with that Device-Interface to steer a rotor.
But this all might work on a TwinHan-Card ! ! !
To implement same features and capability for Technotrend (and other same like OEM's) it is nessecary to implement the TT-API also as well. I need to have each OEM's SDK and implement it.
DD (and tools / modules / interfaces) is freeware and will be developed after work."
It seems that many issues are related to immature BDA-driver architecture implemented by MS so far. Some issues with 7500 may be resulting from DVBDream developer not having this tuner yet at hand. It may benefit the outcome, if you try XP SP3 and especially Win 7 with improved BDA support.
I've sent your report on DVBDream 1.4i issues to Prof, but I think resolving issues of this obsolete version is a dead cause. Pls post your findings with DVBDream 1.5.7b in DVBDream beta forum, and findings with DVBDream 1.4i in their regular forum, as their developer asks. Sure, it'll be fixed faster this way compare to resolving via Prof. Try running 2 sessions of DVBDream 1.5.7b to see, if it supports 2 identical Prof tuners this way. I "think", TeVii shown the pics of this version with their 2 tuners S660, which was posted in DVB World thread here, if it wasn't a bluff.
On DVBDream
Forum there are user instructions on running "multiple instances" of DVBDream. As per Prof, multiple identical Prof cards with BDA-drivers should run simultaneously in this scenario without a problem, no mods required. Pls try. Can you also try 2 identical Prof tuners in ProgDVB or MyTheater to see if both show pics simultaneously.