5730 booting freezes

ZIGZAG

Hi-
In order to replace my fatigued and dead 5730 - 320gb - 4gb, I bought for a few bucks another 5730, with half hd and RAM capacity, rather unused as keys and case conditions sugges.
I used it as it was for a week.
Then I put my old 320gb into the "new" 5730, alongside an additional 2gb bank, in order to top the 4gb max RAM capacity for this machine.
Good. It worked much better, as expected. Windows asked me to verify my software, I did it, everything was fine. Good work for another week.
Yesterday in the morning pc started on its own to perform a memory check, 1 of 2, it said, and it was incredibly slow in doing it, until it stopped at roughly 20% of first step. 
I exited that check, worked the full day, turned pc off in the evening.
This morning booting stopped right after I put password. 3 or 4 times.
Now booting stops before letting me digiting password, as pointer is freezed.
I tried to boot holding F2 and then resetting memory to default by F9 key, as I read in this forum for a similar problem, in case in was BIOS battery (?), but to no avail.

Help me, please. 

JackE

>>>alongside an additional 2gb bank,>>>

Remove one 2GB module and try booting again on a single 2GB module. If it still doesn't work, try the other single 2GB module.  Jack E/NJ