[angvelem]

Ну правильно, у тебя проверяется только на CapsLock без учёта других клавиш

Код:

  fEatKeystroke := (p^.vkCode = 20);

а как же это?

Specifies the extended-key flag, event-injected flag, context code, and transition-state flag. This member is specified as follows. An application can use the following values to test the keystroke flags. Value Purpose
LLKHF_EXTENDED Test the extended-key flag.
LLKHF_INJECTED Test the event-injected flag.
LLKHF_ALTDOWN Test the context code.
LLKHF_UP Test the transition-state flag.

0 Specifies whether the key is an extended key, such as a function key or a key on the numeric keypad. The value is 1 if the key is an extended key; otherwise, it is 0.
1-3 Reserved.
4 Specifies whether the event was injected. The value is 1 if the event was injected; otherwise, it is 0.
5 Specifies the context code. The value is 1 if the ALT key is pressed; otherwise, it is 0.
6 Reserved.
7 Specifies the transition state. The value is 0 if the key is pressed and 1 if it is being released.