Do I need a new power supply after this upgrade?

New here and not very computer savvy.

I just added a 2nd hdd to my 10 year old PC and wondering if I need to upgrade my power supply or if I can "get by" with the existing power supply (250 watt rated). It's a general purpose PC and I don't do any gaming.

Can someone take a look at these specs and let me know?

The original drive (master) is a 160 GB, Ultra DMA, 7200 rpm (IDE/ATA).
The new drive (slave) is 500GB.

Here are the rest of the specs for my HP Pavilion a350n Desktop PC.
- 2.8 GHz Pentium 4 processor
- 160 GB hard disk drive
- RAM: 2 GB (SDRAM)
- Windows XP Home Edition
- ASUS motherboard
- CD-RW: 48x (read), 48x (write), 24x (rewrite)
- DVD+RW
- Graphics Card: nVIDIA GeForce4 MX
- Graphics RAM: 64 MB

HDD's only use a lot of power (10W or so) on spinup. OUtside of that, it only uses a couple watts.

Short answer. No.