My computer running slow, when I open tasks manager the CPU usage was off the charts! I thought it was Virus so i scanned wit Avast and no virus was found!  Also the Svchost was also using alot of Mem any idea wat could cause this? Thnks

I could swear I read somewhere that high memory usage by svchost could indicate the presence of a virus, but don't quote me. Also it may be neccessary to scan your PC with multiple AV/spyware utilites to find the culprit as 1 may find what another 1 misses. I realize Norton isn't that popular because it's said to be a resource hog, but to my knowledge I've never gotten a virus on a machine Norton was on!!!

 Avast is good.  Do a boot time scan.  Just click the little arrow on the top left to get to the menu.  There are some other free AV out there that you can use as a secondary scanner.  This was a while back, but I once installed AVG and Avast on the same machine, and didn't see any conflicted.  AntiVir is suppose to be a really good free AV, but every time that I tried it with Avast I got a conflict.   BitDefender works fine with Avast since the free version is just a scanner. 

You might also want to try scanning for spyware.  I like to use AVG anti-spyware and Spybot.  You can also get SpywareDoctor for free with Google pack, but its kind of a pain to turn off, and when its running in the background it uses 30 to 50mb of RAM.  You can also get a Norton scanner with google pack for free.

I have found that certain programs will max out my CPU sometimes.  I have seen CPU-Z max out my CPU before for some odd reason. 

her take a look at these
 http://www.techsupportalert.com/best_46_free_utilities.htm#2
http://www.techsupportalert.com/best_46_free_utilities.htm 

 If your computer is slow, then i would check how much free RAM you have on startup.  Just after your computer starts up, go to start, programs, accessories, system tools, system information, and scroll down to see how much free RAM you have.  If you have less than 100mb of RAM free, then your computer will be slow.  Likely the high cpu usage will be the processes trying to run while waiting for the parts they need to run to be pulled from virtual memory, and in the mean time they will sit there using all the cpu time as svchost is a critical windows process that gets top priority.

 You can scan your computer with another piece of AV software, but if Avast doesnt find it via a boot time scan then nothing will likely find it.  Do not install Norton, it is the most easily hacked POS virus scaner/resource hog ever.  There are literally thousands of viruses that can be installed on your system if you run Norton because they have been coded to bypass Norton to install, and then disable norton so that it looks like it is running and it isnt.  I have used Avast to clean up hundreds of systems that had Norton installed on it who swore up and down that they didnt have a virus cause norton didnt find anything and it was up to date.  Avast would always find about 10+ that norton couldnt catch that would have their systems messed up and why i was called over to fix it.
 

I scan it wit avast before many time but still no result

CPU spikes happen when the little gremlins inside the CPU wreak their havoc.