system slow working

When you boot up your machine, ?what programs are automatically loaded?

open command prompt and type "msconfig" there check for the programs which are loading on the startup..unselect all unwanted programs..defragment your hdd..check for any spywares...delete all temp files...

There are diffrent reasons why the system work slow.Do the following steps to rectify your problem.
1.There is a chance that your m/c may be affected with virus.Boot up from a virus free disk and use any antivirus(with latest update) software to check and clean if there is any virus.
2.If it is not virus related problem then it could be a Hard Disk drive related problem.
Run Scandisk or any diagnostic program to check if there is any bad sector in your Hard Disk.If the bad sectors could not be removed by scandisk then be prepared to change your HDD.Also defrag your HDD regularly.
3.Remove unnecessary programs/files from your HDD.
Remove Windows Themes and animated cursors if there is any.
If still the problem is there after the above steps, try with another memory card.

Above are good suggestions, order I use is;

1 Check MSConfig and un-check all unwanted/unused (especially messenger/mail services as they will be trying to access the server bogging down the CPU) programs from the startup tab, this will request a re-boot to boot with new settings.
2 Search for and delete ~*.* (MSOffice), *.tmp (MSOffice/downloads), and FFF*.* (IE upgrades have been known to create these type of files in the windows directory killing performance then empty recycle bin.
3 scandisk
4 defrag
5 Check diskspace available for WIN.SWP Swap file under 10% or in your case under your ram 128Mb on the HD open look at replacing or adding a larger HD.
6 reboot and see if system is faster
7 check for spyware in any case
8 virus scan recommended
9 reboot and see if system is faster
10 go through directories and see if any have over 1000 entries especially windows (move all *.doc and *.xls files found in the windows and c:\ to a different sub-directory), fastfind will greatly inhibit performance. Win 98 slows dramatically when trying to view the directory with over 512 entries.

I'm assuming the PC was working fine at some point?

Some pointers;

1) Check for programs in startup group
2) Ctrl/Alt/Del and check for running programs
3) Run msconfig and check for startup entries
4) Check you have sufficient free disk space an the system partition
5) Scan for viruses
6) Run scandisk and defrag
7) Delete *.tmp files
8) If the PC has a history of programs being installed/uninstalled on a regular basis (e.g. coverdisks) consider running a registry cleaner or better still do a clean install.