About a week ago i hooked up my
Peavey vyper 15Watt amp into my laptop
Through the 1/8 inch insert from the amp
Itself into the 'mic in' insert of my laptop.
It had been working fine until like 30 min later
When my computer froze for some reason i
Dont know. I was not using plug ins or effects
From sonar x1 le.

I have a lenovo i have had for about a year now.
Lenovo Ideapad z570 setup:
-windows 7 home premium, 64 bit
-intel core i3 (2.3 Ghz, 3mb cache) CPU
-4GB RAM
-750 GB, 5400 rpm (hard drive)

Your help would be very apprecciated.
Thank you in advance.

The 1/8 insert is probably at line level and you've plugged it into a mic input which usually, actually always, expects a much lower signal.
 
You might well have blown something in the mic-pre circuitry, but this should not have frozen your laptop.

A level mismatch would cause distortion... but that wouldn't cause the laptop to freeze.
 
Do you have  the laptop tweaked for audio purposes?
How much is running in the background?  Lenovo loads tons of "sludge" by default.
I'd start by "cleaning up" the system (shut down anything that's not necessary).
 
Also, I'd recommend using a dedicated audio interface.
Doesn't need to be expensive, but the performance will be a LOT more solid.
The Presonus Audiobox 22VSL sounds good... and the drivers provide solid low-latency performance.

Thanks guys for the response.
but no, I didn't have nothing running in the background...just sonar.
I haven't tweaked nothing on the laptop. I just straight up hooked up it up.
I began by hooking up the cords from the amp to the computer, while it was on
but the amp was off. Then I opened up sonar with just a single track (for guitar only).
after hooking up the 1/8 inch cord on both ends and setting up sonar...I finally
turned on the amp. everything was cool. sound was coming through...but as Bristol_Jonesey
described...a good sound/signal ran through but then after like a couple seconds...the guitar signal faded
and degraded I think due to the lower signal expected by the "mic in" insert.
I think the "record out" of the amp is at line level and through the process of incoming signal
to the "mic in" insert....the signal degraded. Could the "mic in" insert be also the problem a my
degraded signal?