I'm trying to upgrade the internal hard drive for my laptop since the one I had died. It came with a IDE 40 GB at 4,200 rpm. I wanted to get a bigger HD at 5,400 or 7,200 rpm. I'll probably go for one at 5,400 rpm for more than 100 GB.
The problem is HP says that my model has been tested to support hard drives at 4,200 rpm and I can't go higher than 80 GB either. I've chatted with them online and they aren't very reliable since they've told me different stories. I spoke with the IT guy at my company and he said that there shouldn't be any problems upgrading it something faster than 4,200 rpm but I'm not sure if my BIOS will support it or I'll come across problems. What does anyone think about upgrading to a faster rpm and capacity that the manufacturer suggests?

Also, which brand would you guys recommend? I'd like something fast, reliable and that doesn't overheat since the Pentium 4 that I have already does that.

The specs for my HP laptop are the following:
HP Pavilion XT5366WM
Microsoft Windows XP Home Edition
US product number DC996A#ABA
Microprocessor Intel Pentium 4 - 2.6GHz
Mircoprocessor Cache 512KB (L2 cache)
Frontside BUS speed 400MHz front side bus
Processor architecture
Chipset ATI IPG 345M Northbridge
Hard drive 40 GB
Drive RPM 4200RPM
Memory 512MB DDR SDRAM
Memory max 1024 (2 x 512 MB DIMM)
Memory speed 266 MHz
Total DIMM sockets Two
Available DIMM sockets One
Multimedia drive 24X DVD/CDRW COMBO drive
Diskette drive 1.44 FDD
Modem Intergrated v.90/v.92 56K (RJ11 connector)
Network Intergrated 10/100 BASE-T Ethernet LAN (RJ-45 connector)
Keyboard 88 key with touchpad; 5 one touch internet buttons
Pointing device Touch Pad with intergrated Scroll Zone
Sound 16-bit Sound Blaster Pro-compatible audio; internal Altec Lansing speakers; Volume control buttons and mute button
PC Card Slots 1 Type I/II PC card slot; CardBus-enabled

Any help would be appreciated. Thanks.

I tend to agree with your IT guy... Is Windows upgraded to Service Pack 3? Stay around 100GB to 160GB and 5400rpm. It may run a 7200rpm

should go without saying, but a bios upgrade is probably in order if you are worried about GB of capacity being compatible.