The driver is provided by the operating system since Epson never wrote any XP drivers. Just click on Printers & Faxes, Add New Printer, select LPT1, select Epson, select LQ-100, then follow the on-screen prompts until finished.
If you want to check the Epson website,
#1: Go to: www.epson.com
#2: Select country ---->
#3: Click on: Drivers & Support --->
#4: Click on: Printers --->
#5: Click on: Inkjet ---> (or other applicable printer type)
#6: Select your printer model --->
#7: Select "Drivers & Downloads" (or just click the Windows link)
If your model is not listed then this model probably isn't supported in the selected OS or isn't sold or supported in that country, try another country at step #2
Note: Epson website design prevents direct linking to a driver file.