System slowdowns - what's wrong?

[NiPNi]

I re-installed Win98SE recently, and since then, my computer keeps slowing down *a lot* every now and again. That's incredibly annoying when playing games, I'm sure you can all imagine that. It slows down so much, my old SX25 could have run in circles around it. It happens about every 20 minutes or so and lasts for 20-30 seconds. During those seconds, opening My Computer takes 10-15 seconds, that should illustrate how bad this is.

I have not been able to figure out what's wrong; my system is excactly as before the re-install, and all the drivers are the same.

My system:
- TBird 800@900 (9*100) w/FOP38
- ABit KT7-RAID (don't remember BIOS version, would have to reboot to find it, but it's the first one that introduced the 1.0.3 HighPoint BIOS. The one that came after UL if I'm not terribly wrong)
- 2*128MB PC133 SDRAM (running @ 100+33 MHz)
- SBLive 1024
- Adaptec AHA2940AU (Plextor 40MAX and Teac CD-R55S connected to this one)
- ATI Radeon 64MB DDR ViVo
- 3Com 905B 10/100
- 2*IBM 75GXP 30GB masters on IDE3 and 4, striped.
- IBM 20GB don't-remember-model master on IDE1

That should be about it. Using VIA 4in1 4.25a and HighPoint's 1.0.3b driver.

So, any suggestions? I've tried to re-install Windows a couple of times, that didn't help. This is really annoying, my computer is more or less useless when it comes to gaming now.

Edit: My computer is on a 50-computer LAN. Some of the others on the network say they experience the same thing. Could it be network trouble causing this? I find it hard to believe, as my computer is on a switched 100MBit connection, but I don't know too much about these things. And the network has been kind of bad lately...

 

[jsbush]

What type of nic's are all the computers running on the network? If they are cheep nics they sould all be the same or you could have problems, also if some are running an 10 and others at 100, that's not the best thing.

 

[NiPNi]

There are all sorts of different equipment here. 50 computers and almost as many different nics, ranging from very cheap 10MBit cards to too-expensive 100MBit ones.
Not even the switches are all the same brand. (a little explanation: I'm at a campus where there's no LAN available, so we made our own, stretching out cables through the windows ) Nevertheless, this network has been working flawlessly for 4 months now, and the troubles started just a few days ago, at about the same time I started experiensing the slowdowns.

I take it you think the network might cause the problems?

 

[Usul]

I would look for a bad switch.

 

[NiPNi]

Haven't excactly located the source of the problems yet, but my computer worked a lot better once I disconnected it from the network. So I guess the problem is somewhere in the network. It's a good thing because it means my computer is OK, it's bad because the network is a mess, so actually locating the problem is almost impossible...