When I play flv files on vlc, nero showtime, or itunes they stutter/pause. I recently upgraded divx and itunes. Divx plays the files ok. I uninstalled divx thinking codec problem. But this didn't fix. Could there be a problem with quicktime or itunes. I recently got an iphone so I need to keep itunes.
I ran Gspot codec appliance and I suspect there is a codec problem. Here is a list of installed codecs.

DMO WMVA WMVideo Advanced Decoder DMO Microsoft Corporation qasf.dll --> wmvadvd.dll
DMO MP4S Mpeg4s Decoder DMO Microsoft Corporation qasf.dll --> MP4SDECD.dll
DMO WMV Screen decoder DMO Microsoft Corporation qasf.dll --> WMVSDECD.dll
DMO WMVA WMVideo Decoder DMO Microsoft Corporation qasf.dll --> WMVDECOD.dll
DMO MP43 Mpeg43 Decoder DMO Microsoft Corporation qasf.dll --> MP43DECD.dll
DMO MPG4 Mpeg4 Decoder DMO Microsoft Corporation qasf.dll --> MPG4DECD.dll
DSH UYVY Arcsoft Mpeg Encode Filter ** Codec not registered
DSH Arcsoft Realtime Capture Encoder Filter ** Codec not registered
DSH UYVY Avi Writer Filter ** Codec not registered
DSH DV Video Encoder qdv.dll
DSH Indeo® video 5.10 Compression Filter Intel Corporation IR50_32.DLL
DSH IYUV Ligos GoMotion Analog to MPEG Filter Ligos Corporation GoMotionAnalogToMPEG1_1.ax
DSH YUY2 Ligos GoMotion DV to MPEG Filter (Version 1.7) Ligos Corporation GoMotionDVtoMPEG.ax
DSH MJPEG Compressor quartz.dll
DSH Nero Digital AVC Video Enc Nero AG NeNDVid.ax
DSH MPEG1 MPEG Video Decoder quartz.dll
DSH DirectVobSub (auto-loading version) Gabest DVobSub.ax
DSH MSS1 Microsoft Screen Video Decompressor Microsoft Corporation msscds32.ax
DSH WMV1 Windows Media Video Decoder Microsoft Corporation wmvds32.ax
DSH WMV2 Windows Media Video Decoder Microsoft Corporation wmv8ds32.ax
DSH MP43 Microsoft MPEG-4 Video Decompressor Microsoft Corporation mpg4ds32.ax
DSH DVSD DV Video Decoder qdv.dll
DSH MPEG1 Ligos MPEG Video Decoder Ligos Corporation lmpgvd.ax
DSH Ligos MPEG Splitter Ligos Corporation lmpgspl.ax
DSH MPEG1 Ulead DVD Video decoder ** Codec not registered
DSH IV50 Indeo® video 5.10 Decompression Filter Intel Corporation IR50_32.DLL
DSH IV41 Indeo® video 4.4 Decompression Filter Intel Corporation ir41_32.ax
DSH CyberLink Video/SP Decoder CyberLink Corp. CLVsd.ax
DSH MJPG AVI Draw quartz.dll
DSH Nero PresentationGraphics Decoder Nero AG NeBDGraphic.ax
DSH Video Port Manager quartz.dll
DSH MJPG MJPEG Decompressor quartz.dll
DSH RV20 ArcSoft RealMedia Video Decoder ** Codec not registered
DSH Nero InteractiveGraphics Decoder Nero AG NeBDGraphic.ax
DSH FLV4 FLV Video Decoder Gabest flvDX.dll
DSH AVI Decompressor quartz.dll
DSH ArcSoft H263 Decoder ** Codec not registered
DSH RadLight Theora Decoder RadLight, LLC RLTheoraDec.ax
DSH MPEG1 ArcSoft MPEG Video Decoder ** Codec not registered
DSH QTRpza QT Decompressor quartz.dll
DSH YV12 CoreAVC Video Decoder CoreCodec AVCDX.ax
DSH MPEG2 ArcSoft Video Decoder ** Codec not registered
DSH Nero Video Decoder Nero AG NeVideo.ax
DSH Nero DVD Decoder Nero AG NeVideo.ax
VFW CVID Cinepak Codec by Radius Radius Inc. qcap.dll --> iccvid.dll
VFW I420 Helix I420 YUV Codec www.helixcommunity.org qcap.dll --> i420vfw.dll
VFW IV32 Intel Indeo(R) Video R3.2 qcap.dll --> ir32_32.dll
VFW IV41 Intel Indeo® Video 4.5 Intel Corporation qcap.dll --> ir41_32.ax
VFW IV50 Indeo® video 5.10 Intel Corporation qcap.dll --> ir50_32.dll
VFW IYUV Intel IYUV codec Microsoft Corporation qcap.dll --> iyuv_32.dll
VFW M261 Microsoft H.261 Video Codec Microsoft Corporation qcap.dll --> msh261.drv
VFW M263 Microsoft H.263 Video Codec Microsoft Corporation qcap.dll --> msh263.drv
VFW MRLE Microsoft RLE Microsoft Corporation qcap.dll --> msrle32.dll
VFW MSVC Microsoft Video 1 Microsoft Corporation qcap.dll --> msvidc32.dll
VFW VMNC VMnc v2 ** Unknown VFW Driver file missing

My Rig

My system,
Athlon XP2400 cpu
Gigabyte GA-7vaxp Rev 1.1 mb with promise onboard raid controller Bios Award F8
Serial No. : 010471933173101421sn0240904160
Kingston value ram 1536mb DDR pc3200 400mhz
Dual 80gig maxtor hd's 7200rpm ata 133 raid 0
Seagate 500GB and 250GB external hard drives
Artec 16X DVD-ROM
Cyberdrive 40X16X48 CDRW
Verbatim 2.4X DVD+RW/R
Liteon Superallwrite lightscribe 16/48 DVD/CDRW
ATI all in wonder 8500dv AGP primary video card
Radeon 9250 256MB PCI Secondary video card
2 HANNS-G 28" High Def LCD Monitor HG281
2 Hyundai 19" LCD Imagequest Monitors L90D+
Antec 430 watt true power ps
Ahanix platinum xp steel case
Windows XP Home SP3
Avast antivirus
Sunbelt Kerio Personal Firewall 4.3
Uverse Dsl 18 Mbps

Any advice will be appreciated.