CPU and System Performance Irregular

Hi everyone, my computer whenever running a movie or a game such as WarCraftIII it runs ok for about 5 seconds then lags for about 2 secs. here is my system information and also I will upload a picture showing the CPU activity gathered using process explorer. I hope the image gets posted ok, but basicly it shows a very spiky field of activities, on the top of spike the application would be whatever i was running, such as a movie or a game. in this case would be windows media player. my computer has no virus or spyware as i have checked with various virus scan utilies and spyware utilities. also formated computer, please help me with some suggestions on what to do, thank you

Pentium 4 2.53GHz

1.00GB of ram

ATI radeon 9550

windows XP

OS Name Microsoft Windows XP Professional
Version 5.1.2600 Service Pack 2 Build 2600
OS Manufacturer Microsoft Corporation
System Name JOHNNY
System Manufacturer AWARD_
System Model AWRDACPI
System Type X86-based PC
Processor x86 Family 15 Model 2 Stepping 7 GenuineIntel ~2533 Mhz
BIOS Version/Date Phoenix Technologies, LTD 6.00 PG, 1/22/2005
SMBIOS Version 2.2
Windows Directory C:\WINDOWS
System Directory C:\WINDOWS\system32
Boot Device \Device\HarddiskVolume1
Locale United States
Hardware Abstraction Layer Version = "5.1.2600.2180 (xpsp_sp2_rtm.040803-2158)"
User Name JOHNNY\User
Time Zone Eastern Daylight Time
Total Physical Memory 1,024.00 MB
Available Physical Memory 574.61 MB
Total Virtual Memory 2.00 GB
Available Virtual Memory 1.96 GB
Page File Space 2.40 GB
Page File C:\pagefile.sys
[IMG]
and here is my problem:

http://forums.devshed.com/attachment.php?attachmentid=&stc=1
desktop1.JPG


[IMG]desktop1.jpg[/IMG]

Are you running multiple applications when this happens ?

no just 1 application such as media player or a game, in this case media player playing a movie

that stop and go stuff you see is usually because of hard drive access, have you looked at your lights when this happens, can you confirm that its drive access? if that is the case then i would look into what is accessing the drive, its also possible that your just out of RAM and thats causing it to access he drive

having little space left or a badly fragmented drive can slow down the drive a lot and this will amplify the affect, so how much space do you have left and have you tried a defragment

if it doesn't appear to be drive access then you should really try and find what process is using the CPU, that can greatly help in finding the cause