I installed Kubuntu 8.40 64bit some time ago on my Laptop.

When booting for the first time, i had to add acpi=off to the bootline to avoid that the laptop shut itself down and bring me back to grub.

The system was stable for some time until i forced a reboot by pressing the power button. The error did appear again but this time i could solve the problem by adding noacpi acpi=off nofb in grub to the bootline.

System was stable again, until, you guess it i don't learn easly, i did again a hard reboot.

So now with those options, it wont shut itself down anymore but hangs on the line "io scheduler cfq registered". Removing the lines concerning acpi will reproduce the old problem with shutting itself down.

i tryed all combinations of nofb, acpi=off, noacpi nospash, i could think off.

Also tryed a different vga modus i found as a suggestion.

Beeing a linux noob i'm at a loss of what to try besides installing kubuntu again. which i would like to avoid as this would mean my home directorys would be gone as i understand it.

Well i hope someone has another idear what i can try, thanks.

laptop Specs?

bios settings?

Here the laptop specs:

Intel® Core™ 2 Duo Prozessor T5750 2,0 GHz 667 MHz FSB 2 MB Cache
Chipsatz Intel PM45 + ICH9M

RAM 2x 2GB PC2-5300 (800 MHz), DDR2 SODIMM

NVIDIA® GeForce® 9200M GS 512MB

250 GB SATA Harddrive with 5400 U./Min.

Intel HD Audio Codec, REALTEK ALC262-VC2-GR

The laptop is from Samsung.

I didn't make any changes in the BIOS so far. Any specific settings that i should look up?

Have you tried Kubuntu 32-bit? (And btw, the current versions are 8.04 LTS and 8.10).
Do you really need a 64-bit operating system on the laptop? Unless you have 4 GB or more of memory, then you probably don't. If you have a 64bit CPU you can run 32-bit Ubuntu. I have a 64-bit CPU and I have always run 32-bit Ubuntu.

Since you are a beginner in linux I would recommend 32-bit Ubuntu 8.10. Use the 8.10 32-bit alternate install (text based) CD for the most fail safe install. Or try the 32-bit Ubuntu 8.10 live CD if you feel you need the point & click installer. The alternate install CD is pretty easy to follow though. And 32-bit Ubuntu *may* fix your acpi related problems.

As for your data in home, choose manual partitioning and create 3 partitions: a 10 GB for root, a 1 GB for swap, and the rest for home. You could make root as small as 5-6 GB if you are tight on space. The advantage of a separate home is that all your data is on a separate partition so that when you reinstall (K)Ubuntu all your data is safe. You will need to backup all your data if you repartition your hard drive. But this is a one time thing. Once you have your partitions set up the way you want you can just reinstall Ubuntu to the root partition any time you want and all your data is safe on a separate partition.
Read through this site for getting started with Ubuntu:
http://www.psychocats.net/ubuntu/

And welcome to the LQ forums! Welcome to the cool side of computing!

1. Update your bios to the latest version. That is important

In bios setting enable all 64-bit related settings if any (some of them may be disabled)
Also take a look at the power management section

2. 64-bit Linux (amd64 or x86-64) should be fine on your system