Hi there again Apoorva, sorry for the late reply.
Ok, there are certain ways we can speed up the computer. First
Click start then run, type prefetch then press enter, click edit then select all, right click any file then click delete, confirm delete
Click start, all programmes, accessories, system tools to run disc clean up, then from system tools, run disc defragmenter.
Click start then run, type chkdsk /f /r then press enter, type Y to confirm for next boot, press enter then reboot.
Windows will appear to load normally then either the monitor will show progress or the screen will go blank, do not disturb this. This will take an hour or so before it gets to the desktop.
Click start then All Programs, Accessories then System Tools, click on Disk Defragmenter. Click on C:\ and then on Defragment.
This will take a bit of time. I cannot be sure if this will work, because as I have said before maybe user 1 is more frequently using the internet and downloading things, where as user 2 is just checking his mail. (This is an example Example)
Also if you download TuneUp Utilities 2006
there is an internet optimizer.
Once you have downloaded and installed "TuneUp Utilities", open it and goto "Optimize And Improve", then click on "Tune Up System Optimizer". Once the new window has opened click on "Complete Maintenance on computer", click "Start Scan". The proccess will take a few minuits, when complete click "Correct Problems".
Once again go back to "Tuneup System Optimizer" and this time click on "Accelerate downloads and internet surfind", select your connection type (eg. 56kb), then "Next" and "next" again when done. Then click "Finish", when the message box comes up asking if you would like to restart, click "No".
Open "Optimize & Improve" again. This time on "Tuneup RegistryDefrag. follow the prompts until registry defrag has been completed, restart your computer.
Try and see if there is an improvment in any way, this should make things run a bit faster, not just when clearing your history, but the entire system preformance.