All printers drivers installed on my IBM laptop computer (uses xp pro)  were erased
and windows installer does not function. What happened? How do I fix this?

The first two things that come to mind are:
a) hard disk failure
b) virus

so scandisk (with surface scan if you have the time) and some decent
anti virus program could cast some light on it. Then running some
spyware removal tools is reccomended also. And in what state is you
XP. Already installed the SP2 update?
The fact that the windows installer does not work lets me suspect,
that there are some viruses loose in your system.

After you have verified that, you have no hard disk problesm or virus
infections, is it sensible to further diagnose your problem.

I'd re-install Win Xp over itself, install the SP2 update from
microsoft and get the lasteest drivers from IBM if Xp can find your
printer.

Try going to Microsoft.com and look for the Installer that you are
looking for, then go to the website for your printers and look for the
drivers

Incase system restore option is on then restart the machine and hit F8
and go to safe mode. It will prompt you to get the system to go back
to previous date. Choose may be one week back when things were working
fine. Data is not supposed to be lost and it typically restores all
drivers until this date you selected.

Incase that does not work then you need to reinstall win xp. IBM
laptops are little complex....  It needs all the drivers supplied by
the company when it was bought. It can also be downloaded online from
www.ibm.com, select the type of laptop you have and download all
possible drivers you need.

If you dont have the installer cd, then try F11 or F6 or Ctrl-D or
Alt-D and see if it prompts you for reinstallation. IBM laptops come
with built in extra harddrive space which contains the installation
files.

if you have an ibm think pad then you should have a button saying
think or think pad this is a bule button. when you start you computer
press this and hold it until a ibm uitilety starts up. restore you
compture to factory settings and this will return the compture to the
setings you had when you bought it. this will only work if you have
not deleted the hiden partision on the hardisk.