You need:
More physical memory! Windows XP uses around 110mb just to run so you can see any machine with just 128mb is going to run out very easily.
you just need to go out and buy another stick of memory! another 256mb should speed things up quite considerably.
take the tower down to your local PC repair shop and let them install the correct type for you or go online to:
These people gaurantee 100% compatibility as long as you can ive them all the details .
If you can afford it I would also recommend you buying a second hard drive, set to master and reset your old one to slave (jumper on the back of the units) to give yourself much more storage.
You can pick up an 80gb for as little as £45 ($65?)
Re-installing windows then, is just a case of setting the first boot device in the bios to cdrom, placing your copy of XP in the drive, where it should spin up and start the install process, quick format NTFS and follow through to install.
Martin
It looks like you need it!
Start by questioning and soon you will be anwering.
So please take but remember to return and give when you can.