huge folders/ files consume h/d…what are they?

Acer l/top 7220 series. 160g h/d. i have 2 huge folders (look like maybe sys. files?) now consuming over 90% of h/drive. (win xp pro o.s.) Have deleted all patch b/ups, past restore points, virus vaults, etc., but no major change. folders are named; iIreVKMzd{SDmo’)PZ (using 69% of h/d) and YN987Ue-k~f3KPm4,j (using 28% of h/d).Can any-one tell me what these folders ARE, and can i delete the contents to regain disc space? thank you. Steve.