Ok, ive had DH 0.41 for a while and it worked just fine, then i needed to go to 0.46 to play VCS with the cheatdevice, but it wont work! Which settings do i need? (i have 1.5 fw) , I choose my settings and press start and then it just turns off...what do i do?

Did you use the .46 ultimate installer? Try downloading another GTA iso from someone else.

I would install 3.03 OE-A, its a solid upgrade to Devhook.

I installed 5.1 anyway....what is 3.02 OE-X its everywhere and I have no idea what it is !

3.02 OE (and now 3.03 OE) is a custom firmware by Dark_AleX.
It has all the features of 3.02/3.03 combined with 1.50 homebrew and ISO loading.
So instead of using DevHook, you can play ISOs via the Game section of the XMB.
You can download it from here: http://www.dark-alex.org/

Here's a (non-comprehensive) feature list I wrote a while ago:
- play real UMD games (which require up to 3.03 firmware)
- play real UMD videos (and region-free)
- play ISOs (backed up UMD games) from the Game section of the XMB (and NO-UMD)
- run homebrew that uses the 3.03 kernel (put it in "ms:\PSP\GAME\", where "ms:" is your PSP memory card drive letter)
- run homebrew that uses the 1.50 kernel (put it in "ms:\PSP\GAME150\"); almost all homebrew goes here
- watch MP4 videos (put it in "ms:\VIDEO\" and it will come up in the Video section of the XMB)
- browse the web using the Internet Browser
- play PS1 games using the official Sony emulator
- preventing accidental firmware updates
- recovery mode (hold the "R" shoulder button when booting)

Personally, I would recommend upgrading from 1.50 to 3.03 OE, you won't want to go back (but it is possible to).

I have to start lookin into devhook more I wanna play some isos

Hmm if you have 1.5 just use Fastloader it soo easy for noobs...

Upgrade to 3.03OE-A thanks to adw888 i upgraded and its brilliant thanks mate