|I can think of two possible issue of the top of my head... The first issue could be that your hard drive needs to be fully wiped, zero out; the reason is sometimes a program writes and changes the hard drive partitions. For example if you had two versions of windows like a newer one and older one... ie... WindowsXP and Windows7 on the same hard drive. Windows7 has an upgraded NTFS and it will not work on WindowsXP version.... they are not compatible... A work around is to backup everything on your hard drive to CD or DVD and use a most up to date partitioning utility that excepts Windows7... Furthermore, Linux on the same hard drive as windows can also mess up how the hard drive works... EXT4 will often mess up a hard drive with windows... whereas, EXT3 often works ok.|
1.) Backup your valued files
2.) Buy/Get/Steal a proper up to date partitioning utility that excepts Windows7 NTFS.
3. Completely remove all partitions... ALL.
4. Do not allow for Windows7 or WindowsXP to decide where it puts its self, rather install the OS in the partitions you had created.
5. Remember to make your C drive ACTIVE when you partition...
When a hard drive does not work properly you will get memory and graphics errors and slowdowns.
Also, your power supply at 300 Watts would seem to be enough, but you need to understand that most power supplies operated under their posted Wattage. What this means is that sometimes hardware will not work right or will become a bit flaky causing many problems.
Simple fix, buy a power supply rated at 450 Watts to 500 Watts.
I do not typically give advice regarding systems, but you seem to need it.
Best of luck, :)