iTunes with videos bad, Music & Regular! Crash, Black Screen, Tagging?

So i have been using iTunes for ages and have been collection Music's CD's longer and i got to load them to iTunes a while ago. Music works great in iTunes but with my CD's i often got music video's included so i tried to play them and some regular videos in iTunes and got the following problems and issues (Almost all the tested video files was optimised for iProducts (All MP4 format)) :

1. Can't use some of my music videos (mp4 format) in itunes but i can in Quicktime (Got black screen but good sound ). I have no idea how they coded iTunes but shouldn't they use the same codec's?.
2. iTunes have a tendency to crash if i play music videos in a row. (Like to use random in a music video list, calming in the background. i know it's kind of excessive but i like it).
3. Sometimes i need to play through a music video then reverse back to it to get a picture. (Sound works great tho) .
4. Laggy! Sometimes the sound get out of sync with video and vice versa. (Usually the beginning. Has a tendency to catch up but not always, sometimes a middle lane in the video freezes.)
5. Can't you tag or sort video files better.? My computer sometimes crashes or get changed so i need to reinstall my media library from a backup. It would immensely help if i could ID3 tag media files the same way i can song so they automatically sort in to music video's, movies and Tv-series (media types!) without forcing me too change it in the advance tap at show more information. (This is off topic but i need this for audiobooks too (iTunes don't got my type of books so i am manually coping them from CD to MP3 format and transferring them to my iPhone))

So i'm a trial and error person so i worked a little bit with the problems when i had the time and when finally got somewhere and had some real questions so i created this profile and wrote this post.

Please read the whole post before you go yelling: -Look at this!, Already Asked!, See this forum! It's your computer! I usually get to the point somewhere on this post. At the bottom of the post i have my current specs for my computer. So here comes the wall of text:

I started with this http://support.apple.com/kb/TS1718?viewlocale=en_US and http://support.apple.com/kb/TS1717 which is what you get if you search a bit in apple's support site. Tried all the things there. Disabled Direct3D, Tried Safe Mode On (Note: These two made the performance worse not better.), Checked display colour quality (Maxed), Turned on DMA, (A slight improvement still issues.) and finally got to ReadyBoost. I have all my media on an external drive (Aha you says!) and yes i finally figured out that iTunes can't handle files of that size from a regular external (Observe i do not have ReadyBoost on my 1T drive, It says it don't have the necessary performance). So i moved my video files to my internal drive and it significantly improved in problems 2,3,4 (Not gone!), Also noticed that i need to have as short pathway as possible (smaller improvements yet again!) (None of this shows in troubleshooting, Apple needs to read my post i think.)

I am now browsing web forums for a better suggestions on the problems and found that Apple either did not care about the problems or the members of this or other forums recommended other media player's to use for handling devices and media (MediaMonkey, doubleTwist and so on). Either as to further their own agenda or that they have giving up on iTunes as a media player for large number of media files. (Found a good media tagger, Magic MP3 Tagger, which worked wonders on some of my older albums with no or little information). So back to my problems or questions.

1. What can be the trouble with a mp4 format?
2. Tendency to crash, is iTunes really that unstable?
3. Play through music video to see picture. Really iTunes?
4. Laggy! don't know what more to say or fix. (iTunes take to long to buffer (got between 0-15 seconds delay after i come this far, better then before but not great)
5. Sort video files better. (Tags). The only format i know to date that instantly recognise what media type it is, some movie format and the ringtone format m3u (Useful to know is that you can make your own ringtones by creating a ACC with a limited play time in advanced tab (max 30 seconds) then change the last file ending of the ACC file now created to m3u. Viola! (Don’t forget to change back to the regular playtime on the original file) your custom created ring/smstone in workable and high quality, but i digress).

Sorry for the long read but i wanted to be as thorough as possible and please forgive any grammar and spelling problems. English is not my native tongue and the spelling checker did not work in my laptop (browser) on this website

Currently using (The one with iTunes and the external hard drive) (But have had two different computers before with same problem, 1 PC & 1 Mac):

Screen

SyncMaster T240

Videocard

ATI Radeon HD 4870 (512Mb)

PC

ACPI x86

Motherboard

ASUSTeK Computer INC (P5G-PRO)

Memory

Type DDR2 Dual

Size 4096 MB

External Harddrive

WD Ext HDD 1021 USB Device

IDE ATA/ATAPI

Standard-Dual Channel PCI IDE

Standard-Dual Channel PCI IDE

Soundcard

TerraTec Aureon 5.1 PCI

AMD High Definition Audio Device

Processor

Intel(R) Core(TM) 2 Quad CPU Q8200 @ 2,33GHZ