I have bought and installed both BGs but I have some issues with characters' speech: the game "cuts" the first words in each sentence. For instance, when entering dialogue with Winthrop, I only hear "...hotel's as clean as an elven arse!"
It is quite annoying, as I lose most selection sounds. It is the same with sound effects, such as door openings and spell castings.
Can anybody help me, please?

Are you playing vanilla, or BGT/TuTu? It might also help to post your entire baldur.ini here.

By "playing vanilla" you mean "without mods or add-ons", right? I just downloaded the two games and unpacked them.
It might be interesting to note that I had the same problem with the CD installed versions, that is why I came here to buy the newest versions.
The strange thing is that, on this very same PC, both games used to run smoothly and, as far as I know, I did not change OS (still WIN XP) or soundcard...

This is my baldur.ini file. I did not change anything, of course.

[Alias]
HD0:=C:\GOG Games\Baldur's Gate
CD1:=C:\GOG Games\Baldur's Gate\data\
CD2:=C:\GOG Games\Baldur's Gate\data\
CD3:=C:\GOG Games\Baldur's Gate\data\
CD4:=C:\GOG Games\Baldur's Gate\data\
CD5:=C:\GOG Games\Baldur's Gate\data\
CD6:=C:\GOG Games\Baldur's Gate\data\
[Program Options]
SoftSrcKeyBltFast=0
SoftBltFast=0
SoftSrcKeyBlt=0
SoftBlt=0
SoftMirrorBlt=0
Translucent Shadows=1
Maximum Frame Rate=30
Path Search Nodes=4000
Tooltips=45
Sprite Mirror=0
Gamma Correction=0
Brightness Correction=0
Volume Movie=80
Volume Music=30
Volume Voices=80
Volume Ambients=80
Volume SFX=80
Strref On=0
BitsPerPixel=32
[GameSpy]
Region=0
[Program Options]
Volume Music=40
[Game Options]
Memory Access=100
Footsteps=1
Weather=1
Memory Level=1
Mouse Scroll Speed=28
GUI Feedback Level=5
Locator Feedback Level=3
Bored Timeout=3000
Always Dither=1
Subtitles=0
Keyboard Scroll Speed=70
Command Sounds Frequency=2
Selection Sounds Frequency=3
Effect Text Level=63
Infravision=0
Tutorial State=1
Attack Sounds=1
Auto Pause State=0
Difficulty Level=3
Quick Item Mapping=1
Environmental Audio=1
[Config]
CacheSize=240
[Movies]
BG4LOGO=1
TSRLOGO=1
BILOGO=1
INFELOGO=1
INTRO=1
DEATHAND=1
[MissionPack]
HardDrive=1

I notice a duplication of a sound option in there. I don't know if it would cause any problems, but it would be best to remove the second entry. This is what you have:
[Program Options]
Volume Music=30

[Program Options]
Volume Music=40

Remove the second [Program Options] and the music volume entry.


As mentioned by DeMignon, also try disabling environmental audio:

[Game Options]
Environmental Audio=1

Change it to
Environmental Audio=0

Bingo!
It did work!

Thank you so much for helping me!

Goodbye and happy new year!