Not directly an answer to your question but maybe to your problem. If you connect to the Internet using a router, try enabling its DNS feature and using it as your PC's DNS server. Now on the router, have it default to your ISP's DNS server, but have a second (third) option of 8.8.8.8 and/or 8.8.4.4. That way, if the ISP's server doesn't answer, the router will try the backup DNS.
Not all consumer routers will allow this, but if yours does it will work around the problem.
You could also make 8.8.4.4 or whatever your PC's secondary DNS, used only if the primary is not available. Under *nix-type OSes this requires a very simple step: add one line to the /etc/resolve.conf file. I don't off the top of my head know how to do it under Windows.
Actually the elegant solution is to call your ISP's help line every time their DNS goes down, until they fix the problem.
2If the DNS servers from your ISP gives you trouble why not using an other DNS server? I think the DSN server from Google is located at 8.8.8.8 or 8.8.4.4. – JordyOnrust – 2011-06-07T10:20:55.997
@Bright010957:I remember reading somewhere that using public DNS can lead to some speed problems when using CDN services(like youtube etc.), because in their case they use DNS to redirect to a server near your location. – apoorv020 – 2011-06-07T10:24:16.227
Why not change the DNS servers you are using? Pick a more reliable DNS server. – Moab – 2011-06-07T10:36:56.103
@Bright:Found the relevant slashdot article http://apple.slashdot.org/story/10/12/31/0110226/Beware-of-Using-Google-Or-Open-DNS-For-iTunes
– apoorv020 – 2011-06-07T13:25:37.797