Help! why is my pc encoding so slow?

okay before i begin i should mention my specs so you can see where im coming from

hp pavilion dv4-1120us notebook
intel t5800 cpu @ 2.00ghz
4 gb ram
vista home premium 64bit
250gb hdd 5400rpm

okay so i use dvd flick alot to encode my movie files and burn them to dvd which usually takes exactly 1 hr ( all together) i takes 15 mins to burn the actual encoding of video and audio takes about 30min for a 90 min video

starting last month it has been taking me 2 hours + to complete on similar sized videos

ive done everything, mind you im no amateur with pc's. i though maybe the latest release of dvd flick was making me so slow so i searched the far corners of the web for an earlier release and it cut the time by 10 minutes maybe at most. i used cc cleaner and defragged my hdd. i even installed windows xp and still no luck.
i unistalled all crapware mostly with pc decrapifier. after that didnt work i used restore disks to restore back to original state with vista, ran pc decrapifier, defragged and cc cleaned. nope still 2 hrs. i reseated ram and dusted cpu fans.

fyi this computer is a little over a year old, and for a good year it has been encoding alot and still kept up untill last month

my only thought now would be maybe its a heat issue since the fans are pretty loud now. i might reapply thermal paste with some artic silver 5. and i had already planned on upgrading my processor to a intel t9600 or t9900, i'll get of ebay. i know it will work because hp originally offered those processors with my notebook

any help is greatly appreciated!