Asalam o alaikum !

mera system may ye problem hai k windows XP install karne k kuch din baad achanak se bohat he Slow (like 486 system) hojata hai
or agli dafa win install karne pe ya SYSTEM RESTORE ka backup lene pe sahi hojata hai
at least 10 times try karliya her bios ki setting say, or kam say kam software installation say..
merey system may latest security hone ki waja say koi virus/malware/trojans nahi..
System Config :

Core 2 duo 2.8 Processor
2 GB Ram
1 TB Hard Disk

koi expert iss solution k baaray may bataai

Regards & Best Wishes