there are a lot of online virus checkers that will allow you to scan your pc from uninfected programs search for "online virus scan" for them . try to use the ones WITHOUT a download . this will confirm the existance of any virus you may / maynot have on your pc . Though most of these sites dont fix the issue unless you then buy their software.
an alternative to this problem of slow or complete inability to open some web pages can be due to a number of issue's updates for instance or web security setting. and in worst case senerio virus/adware , however adware usualy works in the way of downloading or changing setting so adverts can be displayed on your pc , some of the worst types actuyaly download other adware without your knowedge.
as for security if you know where to look there are plenty of FREE programs out there which will aide your security i will offer up some names you can check , these are only ones i have had experiance with, however which you choose if any would be your choice entirely and im making no actual recommendation. comodo do an excellent firewall , avast anti virus , Ad-aware protection for advert software , and so on all these can be got for the home user absolutely free and there are of course many other providers though i would search the web for comments people have made regarding the software as there are bound to ones that come pre-infected , such being the world and deviousness of these programmers who write the inicial programs to cause us all issue's.
So with that said even if you have issue's there is no reason to actauly spend money and all sales calls should be treated with the contempt they deserve. " sorry sales calls are a pet hate of mine "
hope this helps .