Can't figure out problem with new PC

Question

Hi all, I just built my first PC and everything's running pretty well with the exception of some lag and freezing.  My mouse and keyboard sometimes lag behind my true movement.  The mouse does this more often and will lag behind for a second before it catches up to my true movement.  Also, the system has occasionally frozen with the image still on the screen (no blue screens).  Finally, when trying to play music, the audio will skip out every 10 or 12 seconds.  Otherwise, the system is working fine... I've been burning DVDs with it and programs run fine on it.
I'm thinking that it has something to do with the RAM.  Here is what I've done so far:  I have all the newest drivers from MSI and Sapphire.  I've tried running the system with each of the 512MB modules by themselves.  I've also tried putting them in different DIMM slots.  Any features in the BIOS that may slow the system have been disabled.  The system runs right around 37C for CPU and 42C for the system, so overheating is not an issue.  The RAM isn't getting too hot because the system is slow right from a cold boot.  I've done memtest and it has showed the RAM to be good.  I also ran CPU-Z and the memory specs are below.  Does anyone have suggestions as to the cause of these problems and how to fix them?  Thanks in advance for the help!
CPU-Z memory specs:
CPU-Z version 1.22
Memory Modules Serial Presence Detect (SPD)
Module #1
General
Memory type      DDR-SDRAM
Manufacturer (ID)   Kingston (7F98000000000000)
Size         512 MBytes
Max bandwidth      PC3200 (200 MHz)
Part number      K
Attributes
Number of banks      2
Data width      64 bits
Correction      None
Registered      no
Buffered      no
Timings table
Frequency (MHz)      133   166   200   
CAS#         2.0   2.5   3.0   
RAS# to CAS# delay   2   3   3   
RAS# Precharge      2   3   3   
TRAS#         6   7   8   
Module #2
General
Memory type      DDR-SDRAM
Manufacturer (ID)   Infineon (C1494E46494E454F)
Size         512 MBytes
Max bandwidth      PC3200 (200 MHz)
Part number      64D64320GU5B      
Attributes
Number of banks      2
Data width      64 bits
Correction      None
Registered      no
Buffered      no
Timings table
Frequency (MHz)      133   166   200   
CAS#         2.0   2.5   3.0   
RAS# to CAS# delay   2   3   3   
RAS# Precharge      2   3   3   
TRAS#         6   7   8

Answer 1

I now have all my programs loaded back on and all the drivers loaded and still have no problems with lagging or audio skipping.  I did not install any of the Promise drivers this time.  All I installed was the via driver necessary for installing windows xp at the "F6" menu.  I also did not install all of the MSI utilities, etc. this time.  SO all I can think of is that the problem lied in the promise drivers or some of the MSI utilities.  The PS is running all of my drives fine as of right now.  Regardless, I'm up and running good, so I'm happy.  I hope this helps someone else.
Also... has anyone had problems with the Realtek ethernet adapter?  My comp. gives me a "network location no longer available" error every time I try to copy files over the network from my other computer.  I haven't seen anyone else with this error or found how to fix it.  I have file sharing enabled, the windows firewall is not on, TCP/IP is installed along with client for Microsoft networks.  They're all in the same workgroup also.  I can connect to the Internet and the connection seems to be set up properly.  I think that covers everything I've checked...