Sorry for the delayed response. Your best options for improving your current rig are to upgrade the DRAM and drive. For the DRAM, you could add a 4GB stick or replace your current stick with two 8GB for a total of 16GB. That will help speed things up in general, and for photo and video editing in particular. Replacing your current HDD with an SDD will put some serious zip into your startup and file retrieval. From the specs, it looks like you have a SATA II drive, but SATA III drives are backwards compatible so they'll work. You can also transfer both to a new laptop, as long as they're compatible.
For the DRAM:
http://pcpartpicker.com/part/gskill-memory-f31600c9d16grsl
For the SSD:
http://pcpartpicker.com/part/samsung-internal-hard-drive-mz7te500bw
That's about $150 for the Corsair DRAM and $250 for a 500GB Samsung 840 EVO SSD, so smack-dab in the middle of your budget. You can go smaller and cheaper, but both of these are very good. One variation you could look at is to get the 250GB 840 EVO for $130, and pick up an HDD caddy. You could remove your operating system from your HDD, mount the HDD in the caddy, then install that in place of your CD/DVD optical drive. That would give you the SSD for OS, applications and currently working files, and your 750GB HDD for media storage.
Neither of these is going to do a whole lot for your gaming experience, but they'll definitely improve your overall computing experience.
As a side note, every variation of your laptop that I've found online has a discrete GPU listed. There's a nifty program called Belarc Advisor (link below) that will tell you just about every important detail of your PC. Try downloading and running it. When you get the report, the first part is a full breakout of your hardware. If you can copy and paste the info listed under "CPU", "Main Circuit Board", and "Display", into a post, that would be helpful in identifying any other options for upgrading.
http://www.belarc.com/free_download.html