Think I've now resolved the second problem with my laptop and felt I should post what I have learned for the benefit of anyone else that may be having problems. This will also help you avoid future problems.
1. Inspiron XPS computers with HT. HT is short for Hyperthreading. This just means that there are two processing cores in the same chip. This is similar but not quite like having a dual processor system.
However, Windows XP treats them as two distinct processors and loads a separate driver for each. It appears that somewhere around the time that XP SP2 was installed, the driver for the second processor was not updated. 
This causes a nasty timing sync issue that causes jumps in performance. You will most likely notice this as strange slow downs in performance that you can't really pin down to any particular momemnt in the game and that is not exactly reproducable. The fix is simple. Go into the control panel/system/hardware/device manager. Expand the processor branch. Select properties for the first processor and select the driver tab. Click on the Update Driver button and just allow windows to search for new driver. The driver was already installed in the system directory but has not been updated for this device. Repeat for the other processor.2. The second problem appears to be a chronic problem with all Dell Laptops.
The fans/heatsink assemblies on laptops make fairly decent vacuum cleaners and tend to pick up all dust on and around your desk. You can avoid this problem by about once a month blowing air back thru the outlet vents while the laptop is off to force this accumulated dust back out thru the fans. This will prevent the build up of dust on the heat sinks which will cause your laptop to overheat and run slow. If it has been 6 months or so since you've done this or have run your laptop in dusty environments, you will need to take more drastic actions. If you aren't familiar with taking apart/putting back together electronic equipment then you'll need to find a geek friend to help you. The Dell manuals (at least the one I have) is very helpfull in providing step by step instructions on how to take apart your system. Look for the Heatsink/Heatpipe assembly removal instructions and follow them exactly. Once you have this assembly removed you can then use a brush to help loosen the accumulated dust (my fins where about 90% blocked with dust). Then blow out the fins to removal any remaining dust. You will need to clean off the thermal compound from both the processor and the heatsink and apply new compound. Do NOT reassemble the laptop without applying new thermal compound. This should eliminate the overheating issues however you will need to continue to blow out the dust on a monthly basis. The canned dust removal spays work great for this.Also, there is a nice utility for Dell laptops to monitor temperature. You can get it here: http://www.diefer.de/i8kfan/indexd.html
This web site is in german so you will need to download this file http://www.diefer.de/software/i8kfangui220.exe
If you have any of the following laptops:
Inspiron 9100
Inspiron 9200
Inspiron XPS
Inspiron 6000
Latitude D610
Latitude D810
Precision M70
You will also need http://www.diefer.de/software/i8kfangui220a.reg
Install the exe file and then double click the reg file to update your registry. This last just modifies settings to make fan speeds read correctly.
Not sure if this is all the problems, but will update this if anything further crops up.
