Free complete fix for windows 7 with issues!

My Dell Inspiron Windows 7 Home Premium is running terribly iv no idea about the admin passcode ( was given 2 disks with hand be down laptop both handwritten on - one says password recovery windows7/8 boot disk the other pc log in now 2.0) previous owner is uncontactable at present as theyre too embarrassed to talk further regarding this poorly running laptop they kindly passed onto me as they upgraded to a new one and i got the old thinking all was well.... Until im told by a tech 1800 number and $200 fix it charge that along with missing system files ( accidently deleted by previous owner) theres "zues" malware along with network problems, 0643 alert when trying to update, doesnt connect to samsung mobile using Kies ( malicious ....) etc etc. I cannot afford any paid diagnosis/repair and was caught by suprise that theyre isnt a comprehensive free diag/fix i could download( far as iv seen that is). At this time iv considered factory reset although techie advised strongly against that and Dell F8( sytem restore?) isnt an option seeing prev owner cant recall admin passcode and iv no idea really what the 2 disks she gave with pc n bag n charger etc are for let alone how to find or recover the password if infact its on one of these disks.

I sincerely appreciate your having read this and realise what a headache it is and would appear to you the reader, so i thanku again and would love very much if you could help me with a simple easily understood and followed fix for my poor laptop as im a complete novice esp with files etc but i do try my best and have done so for several months before reaching out for help. However if you wish to run for the hills after reading my quest i completely understand and sincerely thanku for your time anyway.

Thanku regards

Jo Eldridge

jobaby_78@outlook.com

God Bless ;)