I bought a domain on 15th december and now its pagerank 4 !

No mate! I used autoblog plugin to add videos and it did it

 

Its not tarantulasrecords and yes i have some squidoo lenses but i didn't did blog commenting. I added link in the forums in which i am a member. But my secret is still with me And i removed motorolafans as some copyright issues may have got arisen. I got this advice from here -
http://forums.digitalpoint.com/showthread.php?t=1614150
Again, i used a autoblog script to add some videos from youtube and it used dates from youtube.

The old site was always pr 0 and i used a free host at that time. I have just moved to hostgator.

 

Another guy sent me something link this and it even said pr of google is also fake! Although this one is taking a , long time to load for me.
EDIT 0-
NOW THIS IS SO FUNNY!

 

How do you say that Forum posting and blog commenting are Black hat SEO. Can you tell it detail .

 

Its means that you are urself putting your own site's link on other sites. So it is black hat. But these days a little bit of this works

 

Hey..good job..I also reached to the PR 4,5 but took around 2 months.. Its good that you did this in 15 days..Nice ..

 

And to make you guys believe i me, i would like to tell you that i have researched a lot about SEO and used many techniques. And most importantly! I kept a balance between content and backlinks to avoid sandbox!