Microsoft owns windows and not circuitcity. Therefore if tomorrow SONY,HP,Bestbuy,Circuitcity go bankrupt , we cannot expect Microsoft to finance them and pay for their heavy losses/bankruptcy and/or vice versa.Microsoft gives pretty decent margin of profit to all these sales companies/stores to sell microsoft products. If tomorrow Apple gets bankrupt we cannot expect circuitcity, dell, hp, lenovo,microsoft to help Apple come out of tremendous debt. Its business, the companies reap what they sow, and there are many factors involved in downfall of an enterprise.
Opening new stores by apple would be gr888888 if sales last longer for their high prices.
Apple is still young to be vulnerable to backdoors as windows but it will get more vulnerable eventually with the passage of time.I am not anti-apple but we here are to help you with ur malware issues. I would say that the antiviruses dont cost much now a days. u can go for either nod32 or kaspersky, both are good.Use free versions of superantispyware and malwarebytes and install add ons ''no script'' and ''wot'' in ur firefox and ''mccafe site advisor''[with nod32 only as kaspersky wont allow its installation in the c drive ].
For more additional layer of protection read and use these free utilities at-----
http://www.geekpolice.net/computer-security-f27/virtual-antivirus-the-best-antivirus-protection-t4043.htm
If somehow u still find ur pc giving any error/issues then the option for u is to start using cloud computing programs like Azure,Ajax,Eye OS,You Os, icloud extra.
Hope that ur Pc will work fine, make sure u update all ur definitions for viruses,spyware and the rest.