ok thank you everybody so far.
 
one last thing: i HAVE GOT an audio interface (Steinberg UR22) which i use for microphone recording
 
BUT i cannot see how in the hell an audio interface would help me to solve my cpu problem??
 
what would you suggest to do? i only know an audio interface is needed to set up a connection between a microphone and the computer, but it is not NEEDED to connect a midi keyboard to the computer. would it help any to connect my speakers to the computer through the audio interface?
 
i hope you're not getting tired, but i'm really clueless about how the audio interface would make any difference here..
 
thanks

An audio interface would not solve your CPU problem. Based on the way your original post was worded, I thought the issue was trying to decide whether you'd be better off spending your money on more RAM or an audio interface.

hm.. this is an example of what i thought a soundcard looked like
 

 
and this is built in into a computer. and i thought either increasing the ram or putting in a better soundcard (picture) could solve my problem.
 
but as it seems using an audio interface additionally can have similar effects than exchanging the built in soundcard of the computer (i have no idea xDD)
 
thanks for your patience with me

In your original post, you asked which would be better: More ram or a better sound card
 
You didn't mention you already had an audio interface, in the original post.
 
You also mention Sonar crashing, and that some VSTs use a lot of CPU.
 
So it seems you have 3 questions:
1) Why is Sonar crashing
2) Why are some VSTs using alot of CPU
3) which is better: More ram or a better sound card
 
#1 Sonar crashing - it may be a installation issue, driver issue, or a bad VST.
#2 Some VSTs use lots of CPU power, but using alot of CPU will not cause Sonar to crash. The worst that can happen is an audio dropout that causes your project to stop playing.
#3 is covered in several posts above.
 
As far as how an audio interface can help with a crash/cpu utilization: internal sound cards on laptops are ill suited for pro audio applications, and depending on the driver, can suck up alot of CPU power when pressed beyond consumer level usage. Interfaces designed for Pro audio are purpose built to handle the demands of pro audio applications.

hm.. ok thanks a lot but no that's not what i meant. here's what i meant:
 
i have Sonar X1 installed correctly
i have got me some new vst plugins that use a lot of cpu
when i use one of them (that's when i play them through a midi keyboard) first of all there is an audio drop out and then sonar crashes and i have to restart it
 
i wanted to know if having more RAM can solve this as the plugins will have more to work with
or if a better soundcard (and btw i'm using an mme32 i think) would help
 
so yeah.. i don't know
 

you need to use the Steinberg AI for ALL use in Sonar, including monitoring - turn off your laptop speakers and use headphones plugged into the Steinberg if you don't have speakers. this will likely solve some if not all of your issues

You've had all the best advice at this point. If it were me I would upgrade to win7 64, and get an affordable external interface. You could access all your ram and get better throughput. 4 gigs and an i5 processor should perform pretty well. Avoid the hard drive as part of the solution. Most laptops have pretty slow drives. Also make sure to optimize your windows power settings.

ok thanks i will try that and see what it does

An external audio interface is for all intents and purposes the same thing as a sound card. Since you're using your Steinberg interface, Sonar (or any other host) is not using the internal sound card at all, nor can it, at the same time.

If you're getting dropouts related to performance (playing more notes or opening more softsynths or fx causing trouble) the likeliest cause in your case is that your CPU has simply reached its limit. You can try to ease up on it by freezing tracks/synths that you're not actively playing or manipulating, or by increasing your audio buffer (which will also increase latency). Beyond that, your only option is upgrading your CPU which usually means getting a new computer.

ampfixer
You've had all the best advice at this point. If it were me I would upgrade to win7 64, and get an affordable external interface. You could access all your ram and get better throughput. 4 gigs and an i5 processor should perform pretty well. Avoid the hard drive as part of the solution. Most laptops have pretty slow drives. Also make sure to optimize your windows power settings.

I would agree... Also, google your specific computer and see how much ram your computer can handle... It probably has 2 2gb sticks right now for a total of 4 gb.  It's quite easy to swap out the 2 gb sticks for 4gb sticks, so you would have 8... maybe google it with winx64bit as specs might reflect 32bit limit not necessarily the actual mother board limit... or google round for "has anyone used 8gb in >>>>> machine...
 
Ram is dirt cheap... so, 1. external usb audio interface 2. win7x64 and 3. swap out memory would give you a nice machine for lots of purposes...