Sounds like she's pushing boundaries/testing limits big time. That's so frustrating!
The natural consequence to dumping water on a laptop is that either the laptop gets fried and is pretty much broken and unusable, so no more laptop for her; or the laptop isn't ruined, just wet, in which case it needs to thoroughly dry out, so she can't use it while it's drying.
The logical consequences I'd employ if my kid did that (and we've got 3 laptops in this house--one for each of us, thanks to hand me downs--but we by no means take them for granted):
If my DS dumped water on a laptop, his laptop privileges would be revoked indefinitely. I'd also limit liquids/foods consumption to only in the kitchen/dining area (away from all electronics) and I'd explain why water and computers don't mix; then we'd brainstorm (to get DS involved in the process) other ways to accomplish the goal of watching the DVD on the big TV--all of which would be less destructive than pouring water on a computer.
Have you been consistent with enforcing consequences/limits? If she's tantruming for half an hour, she's either incredibly persistant by nature (quite possible), or she's learned that if she throws a long enough fit, she'll get her way.
If there are certain things you're dead set on, you need to tell her that. She needs to know that no amount of tantruming will change your mind on those very important issues. However, there are probably some issues that you feel aren't as important/set in stone...would you be willing to reevaluate your stance on those? If a certain issue keeps cropping up, maybe sit down with your DD when she's calm, and discuss it with her to see how she'd like you to handle it...and try to come to a mutually agreeable compromise. The hope is that if she feels you're willing to share some power on some issues, she'll be more willing to accept the limits on the absolutes.
Also, definitely step up the work with talking/reading/learning about emotions--what they are, how to recognize them (how they feel inside; how to spot expressions and body language cues), do lots of role playing so she gets lots of practice identifiying them. Also try to do more work with alternative ways to express her upsets--stomping, banging on pots and pans, drawing, putting on a puppet show to work through it, listening to music/dancing--so that she has more tools in her toolbox than crying and hitting.
Of course, my 3.5yo DS prefers to scream, and will only let me pick him up after the worst is over. So I'd start asking her before you try to pick her up, "Are you ready for me to pick you up?" And if she hits/kicks you after she says yes, put her right back down and get out of striking distance. It's okay if she follows you, but not okay for her to hit/kick. That's one of my iron clad rules, actually--but it took about a year for DS to stop trying to hit me--even though I was very consistent and offered lots of alternatives for him to express himself. Guess that means it's a phase, but you have a right to keep yourself safe from harm.