yeah, unfortunately, you've about hit the wall with improving that box already. Since you are running a 3.2GHz CPU, I'm assuming it is already flipped over to the 400/800 front-side bus speed. It's capable of going to 3.4 GHz (@ $35 at starmicro.com) for an extra punch on the processor, just not sure how comfortable you are with swapping out the CPU.
Long story short, a lot of the older Dells are kinda just on auto-pilot when it comes to system config--you can swap out a few parts and it auto-detects the changes, and you only have a few options for upgrades and that's it.
But...sometimes you get lucky and can manually change a few things to tweak the system a little. Forgive the wall of text, but not sure of your familiarity with some of this stuff, so going to try to cover all the bases--just in case you really want to dig into this. It can be a little intimidating if you're not into this kind of thing, but sometimes it's worth it.
If this system didn't come with a 3.2 GHz CPU and you've upgraded it once already, might be worth it to verify if it is in fact running on the higher FSB. If it's still running off a 266/533 FSB that could be a major gimp to the system overall. When you upgraded your memory, I hope you got PC3200 RAM. If it's still PC2700, that could be bottlenecking the system some as well(CPU designed to run on 400/800 clock, RAM designed for 266/533 clock). If the RAM can't be set to run asynchronously to the CPU bus (ie, 400/800 for the CPU and 266/533 for the RAM), than you're in a pickle and have to underclock the CPU at 266/533 to keep from baking your RAM. It's best if you can run RAM at same bus speed as CPU or faster. I also hope it's flipping over to the ATI card for primary video and not still running the Intel graphics. Even though you may have the monitor connected to the ATI card and getting Video from it, the system could still be exhausting resources sending data to the IGE because the board hasn't turned off the integrated video--not likely, but possible.
Most the time these settings are controlled in the BIOS. You can get into it during startup by hitting the F2 key during POST (Dell logo screen, etc. before you see it's starting Windows--when you here it beep and such). Once you get in there, you should see a page/tab referencing the processor speed (CPU) and maybe the Bus Speed (FSB). Make sure that they are showing values for 3.2 GHz or 3200 MHz and something along the lines of 200, 400, or 800 for the FSB. Different systems represent FSB different ways--they may show it at the core rate or the double/quad pumped rate. You don't want it to be showing something along the lines of 133/266/533, as your CPU is setup for an 800MHz bus. If it's set to 266/533--gonna want to make sure your RAM can run 400/800 (ie, it's all rated PC-3200 and not PC-2700) before you ramp up the FSB to 400/800. I don't recall if Dells allow you to set individual timings for memory, but it's worth checking that out too. If it does, it's most likely limited to just the bus speed or the PC-Spec ratings mentioned above. You might have to run the CPU at 400/800 and RAM at 266/533 if you have PC-2700 RAM--that is if it can run asynch mode--in which case you would want to swap the RAM for PC-3200 if you can find it cheap. I doubt you will have any other options for RAM control, but if you can manually set the bus and multipliers, sometimes you can tweak it a little to boost performance a little.
Edit: NOTE: make sure you know how to reset the BIOS before changing these kinds of settings. Should be a section in your manual about this--may reference resetting CMOS. Usually it's just powering down the system, moving a jumper near the motherboard's battery to short 2 pins, then moving it back. Worst case scenario, you can pull the battery for a while then put it back in. This will reset the clocks and everything to defaults if you have to do this, so don't forget to set the date/time afterwords, or the system may think it's midnight Jan 1, 1980.
Somewhere in there, you should also see an option about on-board graphics--may be simply a reference to VGA or Primary Graphics Controller. Want to make sure it's setup not to use the integrated (onboard, may say Intel, IGE, etc.) video. Sometimes it's just a toggle for enable/disable, but may be able to select AGP/PCI, or Auto/onboard options. Want to make sure that it's disabling the onboard if you can.
Now this one may be one of the most overlooked BIOS tweaks/nerfs for an older P4 system to look for--Hyperthreading. By default, this is often DISABLED. If this was turned off when Windows was installed, it may have installed the Uniprocessor HAL and is not running the CPU at full throttle. Want to double check and make sure Windows has one of the Multi-CPU HAL running. note that even though XP Home originally only supported 1 CPU, it would still take advantage of the virtual second CPU of a hyperthreading processor (not sure if they ever fixed that "bug" in service packs or not). If it's not running a multi-CPU HAL, you might need Windows installation media to change it if the files aren't on your hard drive--to be honest, I don't recall if it makes this change internally or needs files from the 386 files on the install media. If you didn't get restore CD's with your PC, the files are likely on the hard drive, possibly in a hidden/protected folder or drive that you can't write anything into or possibly may be blocked from even viewing alltogether.
You can check this in the Device Manager. Run DEVMGMT.MSC from the run prompt (start/run) or right-click My Computer and select properties. Expand the Computer and Processors categories. If the computer references anything other than Uni-processor or Standard PC, than you are likely good to go on the HAL installation. Next, under processors it should show more than one installed with hyperthreading supported and active in the BIOS--if not, need to turn hyperthreading on in the BIOS. Even though the additional CPU is virtual, it does enhance performance as it allows software to use multi-threading (if it's designed to).
Just an additional word of caution before you turn Hyperthreading on if it's off. Make sure you have a way of restoring your system first if you know you don't have access to install media/files on the hard drive. The OEM recovery option is often a wipe of the drive and rebuilds it to the Put-of-the-Box state. If by chance it needs to update the HAL from installation files and you don't have them available, you might not be able to easily recover the system once it starts asking for them. There are some workarounds for it, but it's not for the casual user to fix. This is one of those things where if Windows' own System Restore Point feature is unable to take care of it, it can require yanking the drive and dropping it in another system to fix it if you can't get your hands on install media.
I know...a lot of junk, but that about covers the bases I think.
Edited, Aug 27th 2010 10:01am by BDHERTZER